Multi-sensor device with an accelerometer for enabling user interaction through sound or image

ABSTRACT

A method for controlling movement of a computer display cursor based on a point-of-aim of a pointing device within an interaction region includes projecting an image of a computer display to create the interaction region. At least one calibration point having a predetermined relation to the interaction region is established. A pointing line is directed to substantially pass through the calibration point while measuring a position of and an orientation of the pointing device. The pointing line has a predetermined relationship to the pointing device. Movement of the cursor is controlled within the interaction region using measurements of the position of and the orientation of the pointing device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/812,339,filed Mar. 8, 2020, now U.S. Pat. No. 11,073,919, which in turn is acontinuation of application Ser. No. 16/582,508, filed Sep. 25, 2019,now U.S. Pat. No. 10,698,502, which in turn is a continuation ofapplication Ser. No. 16/395,802, filed Apr. 26, 2019, now U.S. Pat. No.10,459,535, which in turn is a continuation of application Ser. No.15/696,452, filed Sep. 6, 2017, now U.S. Pat. No. 10,318,019, which inturn is a continuation of application Ser. No. 15/098,099, filed Apr.13, 2016, now U.S. Pat. No. 9,785,255, which in turn is a continuationof application Ser. No. 14/712,788, filed May 14, 2015, now U.S. Pat.No. 9,411,437, which in turn is a continuation of application Ser. No.14/463,405, filed Aug. 19, 2014, now U.S. Pat. No. 9,063,586, which inturn is a continuation of application Ser. No. 14/175,960, filed Feb. 7,2014, now U.S. Pat. No. 8,866,742, which in turn is a continuation ofapplication Ser. No. 13/239,140, filed Sep. 21, 2011, now U.S. Pat. No.8,723,803, which in turn is a continuation of application Ser. No.12/782,980, filed May 19, 2010, now U.S. Pat. No. 8,049,729, which inturn is a continuation of application Ser. No. 11/135,911, filed May 24,2005, now U.S. Pat. No. 7,746,321, which in turn claims priority fromU.S. Provisional Application No. 60/575,671 filed on May 28, 2004 andfrom U.S. Provisional Application No. 60/644,649 filed on Jan. 18, 2005,all of which are hereby incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates generally to devices for making presentations infront of audiences and, more specifically, to devices and methods formaking presentations for which interaction with the displayedinformation through direct-pointing is desired or for which verbalinteraction with the audience may be anticipated.

2. Background Art

Technology for presenting computer-generated images on large screens hasdeveloped to the point where such presentations are commonplace. Forexample, the software package POWERPOINT, sold by Microsoft Corp.,Redmond, Wash., may be used in combination with a so-called ‘beamer’ togenerate interactive presentation material and project for viewing by anaudience. Often, such presentations are held in rooms not specificallyequipped for the purpose of showing presentations, in which case use ismade of a portable beamer in combination with a so-called ‘laptop’computer. Under these circumstances the projection surface may be a wallof the room.

During a presentation it is desirable for the presenter to be able tomove freely in front of the audience while retaining the capability tointeract with the presentation and point to specific features on thedisplayed images. It would also be desirable for the presenter to beable to capture verbal comments made by members of the audience so as toamplify and/or play them back to the larger audience.

In general, interaction with a computer is often facilitated by pointingdevices such as a ‘mouse’ or a ‘trackball’ that enable manipulation of aso-called ‘cursor’. Traditionally, these devices were physicallyconnected to the computer, thus constraining the freedom-of-movement ofthe user. More recently, however, this constraint has been removed bythe introduction of wireless pointing devices such as the GYROMOUSE, asmanufactured by Gyration, Inc.

Broadly speaking, pointing devices may be classified in two categories:a) devices for so-called ‘direct-pointing’ and b) devices for so-called‘indirect-pointing’. Direct pointing devices are those for which thephysical point-of-aim coincides with the item being pointed at, i.e., itlies on the line-of-sight. Direct pointing devices include the so-called‘laser pointer’ and the human pointing finger. Indirect pointing devicesinclude systems where the object of pointing (e.g., a cursor) bears anindirect relationship to the physical point-of-aim of the pointingdevice; examples include a mouse and a trackball. It needs no argumentthat direct-pointing systems are more natural to humans, allowing fasterand more accurate pointing actions.

Indirect pointing devices known in the art include the following. U.S.Pat. No. 4,654,648 to Herrington et al. (1987), U.S. Pat. No. 5,339,095to Redford (1994), U.S.

U.S. Pat. No. 5,359,348 to Pilcher et al. (1994), U.S. Pat. No.5,469,193 to Giobbi et al. (1995), U.S. Pat. No. 5,506,605 to Paley(1996), U.S. Pat. No. 5,638,092 to Eng et al. (1997), U.S. Pat. No.5,734,371 to Kaplan (1998), U.S. Pat. No. 5,883,616 to Koizumi et al.(1999), U.S. Pat. No. 5,898,421 to Quinn (1999), U.S. Pat. No. 5,963,134to Bowers et al. (1999), U.S. Pat. No. 5,999,167 to Marsh et al. (1999),U.S. Pat. No. 6,069,594 to Barnes et al. (2000), U.S. Pat. No. 6,130,664to Suzuki (2000), U.S. Pat. No. 6,271,831 to Escobosa et al. (2001),U.S. Pat. No. 6,342,878 to Chevassus et al. (2002), U.S. Pat. No.6,388,656 to Chae (2002), U.S. Pat. No. 6,411,277 to Shah-Nazaroff(2002), U.S. Pat. No. 6,492,981 Stork et al. (2002), U.S. Pat. No.6,504,526 to Mauritz (2003), U.S. Pat. No. 6,545,664 to Kim (2003), U.S.Pat. No. 6,567,071 to Curran et al. (2003) and U.S. Patent ApplicationPublication No. 2002/0085097 to Colmenarez et al. (2002). Each of theforegoing publications discloses a system for which the 2 dimensional or3 dimensional position, orientation and/or motion of an object, such asa handheld pointing device, are measured with respect to some referencecoordinate system using appropriate means. Such means include acousticdevices, electromagnetic devices, infrared devices, visible lightemitting diode (LED) devices, charge coupled devices (CCD),accelerometer and gyroscopic motion detectors, etc. Although for some ofthe foregoing devices the reference coordinate system may be positionedclose to the display means, no information on the actual position of thepresentation display with respect to the system is used, causing theresulting pointing action to be inherently indirect and, hence, lessnatural to the human operators of such systems.

Other inherently indirect-pointing systems that do not require theposition or orientation of the pointing device to be known includedevices such as disclosed in U.S. Pat. No. 5,095,302 to McLean et al.(1992) and U.S. Pat. No. 5,668,574 to Jarlance-Huang (1997). Theforegoing patents describe indirect-pointing methods that do not providethe speed and intuitiveness afforded by direct-pointing systems.

Direct pointing devices are disclosed, for example, in U.S. Pat. No.4,823,170 to Hansen (1989), which describes a direct-pointing systemcomprising a light source, a position-sensing detector located adjacentto the light source and a focusing reflector that, in one application,is parabolic shaped and is attached to the pointing device.Additionally, procedures are described to calibrate the system. In theunderstanding of current applicant, however, the physical location ofthe position-sensing detector needs to be, at least preferably, adjacentto the display means. The system disclosed in the Hansel '170 patentcannot easily be ported to a room not specifically equipped for thissystem.

U.S. Pat. No. 5,929,444 to Leichner (1999) discloses a system primarilyintended for target shooting practice, but an application as adirect-pointing cursor control apparatus may arguably be anticipated.The system includes transmitting and detecting equipment in a fixedreference base and a moveable pointing device. A calibration routine isdescribed that aligns the detecting and transmitting means while keepingthe pointing device (i.e., a gun) aimed at the center of the target. TheLeichner '444 patent does not describe methods or means that allowdetermination of a point-of-aim of a pointing device on a target ofwhich the size and/or orientation have not been predetermined.Consequently, the system disclosed in the Leichner '444 patent is notsuitable to be used as a cursor control means for projection surfacesnot specifically adapted to be used with such system.

U.S. Pat. No. 5,952,996 to Kim et al. (1999), U.S. Pat. No. 6,184,863 toSiben et al. (2001) and U.S. Patent Application Publication No.2002/0084980 to White et al. (2002) disclose direct-pointing systemswhere the 3 dimensional position and/or orientation of the pointingdevice is measured with respect to sources and/or detectors, thephysical position of which in relation to the display means is presumedknown. Such systems only work in rooms specifically equipped for theiruse.

U.S. Pat. No. 5,484,966 to Segen (1996), U.S. Pat. No. 6,335,723 to Woodet al. (2002) and U.S. Pat. No. 6,507,339 to Tanaka (2003) disclosemethods suitable for direct-pointing that are useful only if thepointing device is physically close to or touching the display area orvolume, for example used with so-called ‘interactive whiteboards’. Someof the foregoing patents describe appropriate pointer calibrationroutines. Such systems are not suitable for presentations where thedisplay surface is out of the presenter's physical reach.

U.S. Pat. No. 6,104,380 to Stork et al. (2000) discloses adirect-pointing system in which at least the 3 dimensional orientationof a handheld pointing device is measured by appropriate means.Additionally, a direct measurement is made of the distance between thepointing device and the displayed image. However, the system disclosedin the Stork et al. '380 patent does not include methods to ascertainthe position and orientation of the display means relative to thepointing device. In the foregoing system, these appear to be presumedknown. This is also the case for a system disclosed in U.S. Pat. No.4,768,028 to Blackie (1988), in which the orientation of ahelmet-mounted direct-pointing apparatus is measuredelectromagnetically. The foregoing systems therefore appear to beill-suited to operate in rooms not specifically equipped forpresentation purposes.

U.S. Pat. No. 6,373,961 to Richardson et al. (2002) discloses adirect-pointing system using helmet-mounted eye tracking means. Thepoint-of-gaze relative to the helmet is measured as well as the positionand orientation of the helmet relative to the display. The latter isaccomplished by equipping the helmet either with means to image sourcesmounted at fixed positions around the display or with means to image adisplayed calibration pattern. Of course, the foregoing system relies onsophisticated helmet mounted equipment capable of, among other things,tracking eye-movement. Moreover, such a system relies on an unobstructedline-of-sight with respect to the display and a substantially constantdistance from the display to the helmet-mounted equipment. The disclosedinvention does not lend itself to be easily used by a human operator inan arbitrary (not predetermined) presentation setting.

U.S. Pat. No. 6,385,331 to 'Harakawa et al. (2002) discloses a systemthat uses infrared technology in combination with image recognitionsoftware to distinguish pointing gestures made by the presenter, withoutthe need for an artificial pointing device. The disclosed system,however, requires the presentation room to be set up with highly tunedand sophisticated equipment, and is therefore not easily ported to adifferent venue.

U.S. Pat. No. 6,404,416 to Kahn et al. (2002) discloses adirect-pointing system where a handheld pointing device is equipped withan optical sensor. In such system either the display is required to beof a specific type (e.g., a cathode ray-based display that uses anelectron beam) or the displayed image is required to be enhanced bytimed and specific emanations. When pointed to the display, a handheldpointing device may detect the electron beam or the timed emanations,and the timing of these detections may then be used to ascertain thepoint-of-aim. The disclosed system is somewhat similar to thetechnologies used for so-called light guns in video games as disclosed,for example, in U.S. Pat. No. 6,171,190 to Thanasack et al. (2001) andU.S. Pat. No. 6,545,661 to Goschy et al. (2003). Of course, such systemsrequire either a specific display apparatus or a specializedmodification of the displayed images. Moreover, an uncompromisedline-of-sight between the pointer and the display is a prerequisite forsuch systems.

U.S. Patent Application Publication No. 2002/0089489 to Carpenter (2002)discloses a direct-pointing system that, in one embodiment, positions acomputer cursor at a light spot projected by a laser-pointer. The systemrelies on the use of an image capturing device to compare a capturedimage with a projected image. As such, the system disclosed in the '489patent application publication makes use of calibration routines inwhich the user is required to highlight computer-generated calibrationmarks with the laser pointer. The system disclosed in the '489 patentapplication publication is not unlike a system disclosed in U.S. Pat.No. 5,502,459 to Marshall et al. (1996). Also, U.S. Pat. No. 5,654,741to Sampsell et al. (1997), U.S. Pat. No. 6,292,171 to Fu et al. (2001),U.S. Patent Application Publication No. 2002/0042699 to Tanaka et al.(2002) and U.S. Patent Application Publication No. 2002/0075386 toTanaka (2002) all disclose systems that can detect a light-spot usingoptical means. Such systems specifically generally require the use ofcomputationally expensive image processing technologies. All of theseinventions require a projection surface with adequate diffusionproperties, as well as some form of optical system with a steady anduncompromised view of the display area. As such, they limit thefreedom-of-movement of the presenter and place limitations on theposition and optical characteristics of the necessary equipment. Also,in some of these inventions fast and involuntary movement of the user'shand may result in a cursor that does not move smoothly or a cursor⋅thatdoes not perfectly track the light spot, causing possible confusion withthe user.

Other pointing systems known in the art may be classified as other thanentirely direct-pointing or indirect-pointing systems. Such systemsinclude one disclosed in U.S. Pat. No. 6,417,840 to Daniels (2002),which is combination of a cordless mouse with a laser pointer. Althoughthis system incorporates a direct-pointing device (i.e., the laserpointer), the method used by the system for interacting with thepresentation is indirect (i.e., by means of the mouse) and thereforedoes not afford the fast and more accurate interactive pointing actionsprovided by some other direct-pointing systems described in some of theforegoing publications.

Another system known in the art that uses both direct andindirect-pointing methods is described in U.S. Pat. No. 6,297,804 toKashitani (2001). The disclosed system is a system for pointing to realand virtual objects using the same pointing device. In the disclosedsystem, the pointing means switch between a computer controlled lightsource (e.g., a laser) and a conventional computer cursor, depending onwhether or not the user's intended point-of-aim has crossed a boundarybetween the real and virtual display (i.e., computer-displayed imagery).Various methods are described to establish these boundaries. Althoughthe computer-controlled light source may be regarded as pointing in adirect manner, its point-of-aim is essentially governed by the systemoperator using an indirect-pointing system such as a mouse. Thus, thedisclosed system does not allow for the desired flexibility afforded bytruly direct-pointing methods.

Other systems known in the art include those such as disclosed in U.S.Pat. No. 5,796,386 to Lipscomb et al. (1998), which discloses acalibration procedure to establish the relation between coordinatesystems associated with a handheld device and, in one embodiment, adisplay unit. The system disclosed in the Lipscomb et al. '386 patentmay arguably be applicable as a direct-pointing cursor control system.The disclosed calibration routine requires the user to register at leastthree 3 dimensional positions of the handheld device with a centralprocessing unit. The disclosed system does not appear to includecalibration methods for the case where the display unit is out ofphysical reach of the system operator. The system is thus not practicalfor use at an arbitrary venue.

U.S. Pat. No. 6,084,556 to Zwern (2000) discloses a head-mounted displayunit that displays information governed by the orientation of theapparatus, as measured by a tracking device. This way, the systemcreates the illusion of a large virtual display that is being looked atby the system operator. Of course, the large display alluded to does notconstitute a projected presentation. Also, no methods are disclosed inthe Zwern '556 patent to establish the relative position of thehead-mounted apparatus with respect to the display.

U.S. Patent Application Publication No. 2002/0079143 to Silverstein etal. (2002) discloses a system in which the position of a moveabledisplay with respect to a physical document is established. The '143patent application publication describes calibration routines in whichthe user is required to activate a registration button when the moveabledisplay is over some predetermined position on the physical document.The disclosed system only relates to 2 dimensional applications and,moreover, cannot be used in situations where the interaction region isout of the system operator's physical reach.

U.S. Pat. No. 5,339,095 to Redford (1994) discloses an indirect-pointingsystem where the pointing device is equipped with non-directionalmicrophone. Also, U.S. Pat. No. 5,631,669 to Stobbs et al. (1997)discloses the inclusion of a nondirectional microphone unit in anindirect-pointing device.

SUMMARY OF THE INVENTION

One aspect of the invention is a method for controlling a parameterrelated to a position of a computer display cursor based on apoint-of-aim of a pointing device within an interaction region. Themethod includes projecting an image of a computer display to create theinteraction region. At least one calibration point having apredetermined relation to the interaction region is established. Apointing line is directed to substantially pass through the calibrationpoint while measuring a position of and an orientation of the pointingdevice. The pointing line has a predetermined relationship to saidpointing device. The parameter related to the position of the cursorwithin the interaction region is controlled using measurements of theposition of and the orientation of the pointing device.

Another aspect of the invention is a method for controlling a computerdisplay cursor in an interaction region. According to this aspect, themethod includes establishing a calibration point having a predeterminedrelation to the interaction region. At least one of a position andorientation of a pointing line is first measured while directing thepointing line to substantially pass through the calibration point. Thefirst measurement is used to constrain a parameter of the calibrationpoint. The pointing line has a predetermined relationship to at leastone of position and orientation of a pointing device. A characteristicfeature of the interaction region is used to establish a property of acommon point of the pointing line and the interaction region measuredrelative to the interaction region. At least one of position andorientation of the pointing device is measured, and the characteristicfeature of the interaction region and measurement of the pointing deviceare used to control the cursor on a computer display image.

Another aspect of the invention is a method for controlling a parameterrelated to position of a cursor on a computer screen image. The methodaccording to this aspect includes measuring a first angle between apointing line and a first line, and measuring a second angle between thepointing line and a second line. The first line is related in apredetermined way to a geographic reference, and the second line isrelated in a predetermined way to a geographic reference. The pointingline has a predetermined relation to said pointing device. A firstparameter related to the first angle, and a second parameter related tothe second angle are used to control the parameter of the cursor on saidcomputer screen image, whereby the cursor position parameter iscontrolled by movement of the pointing device.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a pointing device and base station according to a firstembodiment.

FIG. 2 shows a presentation venue and computer screen.

FIG. 3 shows program steps for selection of appropriate assumptionsaccording to embodiments 1, 2 and 3.

FIG. 4 shows program steps for construction of information set accordingto a first embodiment.

FIG. 5 shows program steps for ascertaining necessary 3D data accordingto a first embodiment.

FIG. 6 shows program steps for control of pointing device elements andcomputer cursor according to several embodiments.

FIG. 7 shows one example of a first embodiment.

FIG. 8 shows a second example of one embodiment of the invention.

FIG. 9 shows a third example of one embodiment.

FIG. 10 shows a pointing device and base station according to a secondembodiment.

FIG. 11 shows program steps for construction of information setaccording to a second and third embodiment.

FIG. 12 shows program steps for ascertaining necessary 3D data accordingto the second embodiment.

FIG. 13 shows a pointing device and base station according to a thirdembodiment.

FIG. 14 shows program steps for ascertaining necessary 3D data accordingto the third embodiment.

FIG. 15 shows projection of interaction structure on horizontal andvertical planes.

FIG. 16 shows a presentation device according to a fourth embodiment.

FIG. 17 shows program steps for sound recording and playback accordingto the fourth embodiment.

FIG. 18 shows an image of calibration point and light spots at thepoints-of-aim.

FIG. 19 shows an alternative embodiment of pointing device.

FIG. 20 shows a prior art: construction of method M for a quadrangle.

FIG. 21A shows the presentation device carried as a handset.

FIG. 21B shows the presentation device being handheld.

FIG. 22A shows the pointing device carried as a handset.

FIG. 22B shows the pointing device being handheld.

DETAILED DESCRIPTION

A first embodiment of the invention will be described with reference toFIG. 1. A pointing device 20 has associated with it a coordinate systemx′y′z′. A portable base station 30 has associated with it a coordinatesystem x y z. Pointing device 20 and base station 30 may be equippedwith coordinate sensing devices, 201 and 301, respectively, that enablemeasurement of the 3 dimensional position and 3 dimensional orientationof pointing device 20 and, therefore, of a pointing line 21 (see alsoFIG. 2) that substantially intersects pointing device 20, all measuredrelative to the x y z coordinate system. Pointing line 21 maysubstantially coincide with the long axis of pointing device 20. Forexample, coordinate sensing devices 201 and 301 may be electromagnetictracking devices, such as the 3SPACE FASTRAK® system, manufactured byPolhemus, a Kaiser Aerospace & Electronics Company, Colchester, Vt.Alternatively, coordinate sensing device 201 and 301 may be based onultrasonic tracking systems such as those used in the LOGITECH 2D/6Dcomputer mouse, commercially available from Logitech Inc., Fremont,Calif. Other embodiments for coordinate sensing device 201 and 301 mayinclude, without limitation, sensors based on LEDs, CCDs,accelerometers, inclinometers, gyroscopes, compasses, magnetometers,etc. Also, combinations of such different types of sensors may be usedto acquire redundant measurements for quality control purposes. Forexample, a controlled-source electromagnetic position tracking systemmay be combined with compasses and inclinometers. Those skilled in theart will appreciate that independent measurements of the Earth'smagnetic field and gravity may be used to enhance the measurements madeby a controlled-source position detecting system. In the invention, anysystem may be used that is capable of determining at least parts of theorientation and position in three dimensions, with respect to coordinatesystem x y z, of a line-segment that substantially intersects pointingdevice 20.

Base station 30 may comprise a plurality of related physical entities,such as described in U.S. Pat. No. 6,608,668 to Faul et al. (2003); forclarity of explanation one of these physical entities will be associatedwith coordinate system x y z and be denoted as base station 30, thecenter of which substantially coincides with the origin of coordinatesystem x y z. For purposes of explanation of the invention, the originof coordinate system x′y′z′ substantially coincides with the center ofpointing device 20, and the z′-axis is substantially aligned with thelong axis of pointing device 20.

Pointing device 20 may also be provided with a light-beam projector 202,for example a laser. The physical position and orientation of theprojected beam of light with respect to coordinate system x′y′z′ may beestablished with suitable accuracy at the place of manufacture of thepointing device 20 and may be presumed to be known. For purposes ofexplanation, the beam of light from the light beam projector 202substantially coincides with the z′-axis. Additionally, one or morecontrol buttons 203 a, 203 b or the like may be provided, as well ascommunication and control device 204. Communication and control device204 may be used to control various features of pointing device 20 andmay also communicate via wire, or wirelessly, with base station 30and/or a central processing unit (not shown separately), such as aCOMPAQ Armada M700 as manufactured by Hewlett Packard Company, PaloAlto, Calif. The central processing unit may also control a presentationwith which user interaction is desired. For clarity. of the descriptionwhich follows, the central processing unit will be referred tohereinafter as “the computer.” Furthermore, pointing device 20 mayinclude an internal power source 205, for example a battery, or insteadmay be connected such as by wire to an external power source.

In addition to coordinate sensing device 301, base station 30 may beprovided with communication and control device 304. Communication andcontrol device 304 may be used to control various features of basestation 30. Communication and control device 304 may communicate withpointing device 20. and/or with the computer (not shown) that maycontrol the presentation images. The communication and control device304 may use wired or wireless technology. In the present embodimentcommunication with the computer occurs via a universal serial bus (USB)compatible device or the like (not shown). Communication and controldevice 304 may communicate wirelessly with a relay device (not shown)that communicates via a USB compatible device or the like with thecomputer (not shown) that may control the presentation with whichuser-interaction is desired. There may be visible markings 302 on basestation 30 that indicate the orientation of one or more coordinateplanes defined by prescribed relations between coordinates x, y, z, aswell as features of the position of the origin of the x y z coordinatesystem. For example, a line may be used to indicate the z-x-plane of thex y z coordinate system, for which the y-coordinate is zero; anotherline may be used to indicate the z-y plane, for which the x-coordinateis zero. Base station 30 may be provided with a level sensing device 303to determine whether or not one of the coordinate planes of coordinatesystem x y z is substantially horizontal. Level-sensing device 303 maymeasure two angles or equivalent characteristics that define theorientation of one of the coordinate planes of coordinate system x y zwith respect to a horizontal surface. Level sensing device 303 can be adevice such as disclosed in U.S. Pat. No. 6,466,198 to Feinstein (2002),which makes use of model ADXL 202 accelerometers sold by Analog DevicesInc., Norwood, Mass. The disclosed accelerometers provide tilt angleinformation depending on their inclination relative to Earth's gravity.It will be apparent to those skilled in the art that many other types ofsensors may be used as embodiment for level-sensing device 303, forexample, capacitance-type bubble levels. See, for example, U.S. Pat. No.5,606,124 to Doyle et al. Finally, base station 30 may be equipped witha power source 305, for example a battery, or may have a connection toan external power source.

Referring to FIG. 2, a projection device 40 is arranged to project animage 50 generated by, for example, the computer (not shown). Theprojection device 40 may be used to generate a projection image 70 on aprojection region 60. For example, projection device 40 may be a 2000lumen projector, model XL8U, manufactured by Mitsubishi Corp. Projectionregion 60 may be a surface, such as a wall or a projection screen. Theprojection region 60 may define a flat plane or a may define a moreelaborate 2 dimensional (20) or even 3 dimensional (3D) structure. InFIG. 2, projection region 60 is shown as a screen, but this is only forpurpose of illustrating the principle of the invention and is notintended to limit the scope of the invention. Alternatively thecombination of projection device 40 and projection region 60 may beincorporated in one and the same physical device, such as a televisionreceiver (cathode ray tube display), liquid crystal display (LCD) screenor the like.

There is a region of space that is designated as a region on whichinteraction with the user is desired. This region is denoted as theinteraction region 71. The interaction region 71 may be flat (planar) ormay be a more elaborate 2D or even 3D structure. The interaction region71 may have features in common with projection image 70 and may beassociated in some way with a computer screen interaction region 51. Inthe present embodiment, however, it will be assumed that interactionregion 71 or a scaled version thereof, is substantially part of orsubstantially coincides with projection image 70. Moreover, it will beassumed in this embodiment that interaction region 71 substantiallycoincides with the projection of computer screen interaction region 51as projected by projection device 40.

For display systems which include a separate projection device 40 andprojection region 60, the optical axis of projection device 40 may notbe aligned with any vector normal to projection region 60. Moreover,projection region 60 may not be flat and therefore may not even be a 2Dshape. Consequently, projection image 70 and interaction region 71 mayin general not be flat or rectangular, even if the imagery generated bythe computer is scaled so as to be presented in rectangular form. Inthis embodiment, however, it is assumed that projection region 60,projection image 70 and interaction region 71 are substantially flat.Furthermore, it is assumed in this embodiment that interaction region 71is substantially a quadrangle and that the associated computer screeninteraction region 51 is substantially rectangular.

Additionally, calibration points 721 a, 721 b, 721 c, 721 d may beprovided that may define characteristic features of interaction region71. For example, interaction region 71 may be trapezoidal in shape, inwhich case calibration points 721 a, 721 b, 721 c, 721 d may definecorners of interaction region 71 or corners of a scaled version thereof.Furthermore, screen marks 521 a, 521 b, 521 c, 521 d may be provided,and may but need not be associated with calibration points 721 a-721 d.For example, calibration points 721 a-721 d may coincide with theprojected versions of screen marks 521 a-521 d and may in this way beidentified by projection device 40. Calibration points 721 a-721 d mayalso be identified by other means than projection, for example by uniquedescriptions such as the ‘upper right corner of interaction region 71’,‘center of interaction region 71,’ etc.

The operation of the present embodiment will now be described withreference to FIGS. 1,2 and 3. A display system is set up at the venuewhere a presentation is to made, which can be a combination of aportable projection device 40 and projection surface 60, for example awall. The display system is connected, using appropriate interconnectiondevices, to the computer (which may be in the base station 30 or locatedelsewhere) that generates the presentation images.

The system user positions base station 30 at a convenient location,preferably not far from where the user intends to make the presentationdisplay. The user may position base station 30 in such a way that one ofthe coordinate planes of the x y z coordinate system is substantiallyparallel or substantially coincident with projection region 60. Thevisual markings 302 may assist in such positioning. Subsequently, theuser connects base station 30 to the computer (not shown), for examplevia a USB compatible device connection (not shown), or using a wirelessrelay device (not shown). The computer may be disposed in the basestation 30 in some embodiments. In some embodiments, the computer mayrecognize the base station connection and start a program, part of whichmay be contained in the communication and control device 304, incommunication and control device 204, or in control logic contained inthe wireless relay device (not shown). Alternatively, the user may berequired to load the program into the computer manually via a CD-ROMdrive, a floppy drive, memory stick (USB mass storage device—not shown)or the like. However it is loaded into the computer, the program mayinitiate a calibration routine that has as its object establishment ofthe shape, position, size and orientation of a defined interactionstructure 72 relative to the x y z coordinate system. The interactionstructure 72 is assumed to substantially coincide with interactionregion 71. The operation of the program will now be explained withreference to FIG. 3.

At Boa the program is initiated. During step Bob a default assumption ismade regarding interaction region 71. Specifically, interaction region71 is assumed to substantially coincide with a well-defined interactionstructure 72 (FIG. 2 shows an interaction region 71 and an interactionstructure 72 that are clearly not identical; this difference is howeveronly meant as an example, and as a practical matter is preferably assmall as possible). At Bob default values are entered for theorientation and position of this interaction structure 72. For example,the default setting may assume interaction region 71 to substantiallycoincide with an interaction structure 72 that is a (flat) quadranglepositioned in a vertical plane that substantially intersects the originof the x y z coordinate system associated with base station 30. Asanother example, the default setting may provide that interaction region71 substantially coincides with an interaction structure 72 that is anisosceles trapezoid of which the parallel edges are horizontal and ofwhich the position is unknown. Using such default values, calibrationpoints 721 a-721 d not only define characteristic features ofinteraction region 71 but also of interaction structure 72.

At 80 c a decision is made whether the default values for interactionregion 71 and interaction structure 72 should be accepted or overriddenby the user. In making this decision, input from level-sensing device303 and visible markings 302 on base station 30 may be used. If thedefaults are to be accepted, the program continues to 80 j, the detailsof which are explained below with reference to FIG. 4. If the defaultsare overridden, the program continues at Sod to 80 i, during each ofwhich the user may override any of the default settings. The user may beaided during any of 80 d to 80 i by a library of predetermined shapes,predetermined orientations and/or predetermined positions, or the usercan be provided by the program with the capability to construct customshapes, orientations and/or positions. In any case, the programcontinues to 80 j.

It will be appreciated by those skilled in the art that once anassumption has been made regarding the shape of interaction structure72, it is possible to construct a set of three dimensionally distributedpoints in space that completely determines the 3D position, orientationand size of the interaction structure 72. The number of points in theset will depend on the complexity of the assumed shape and the ingenuitywith which the points are chosen. For example, a rectangular shape thatis arbitrarily oriented in space is completely determined by a set of 3points that coincide with 3 of its corners, but is also completelydetermined by a set of 8 points, pairs of which may determine each ofthe four edges of the rectangle.

Referring to FIG. 4, describing details of program element 80 j, thecomputer program continues at 90 a, at which a set P is generated thatincludes a quantity n of points in space, each represented as C(i)(0<i<n+1), that uniquely determine interaction structure 72, togetherwith descriptions of their roles in determining this structure. Forexample, if the program elements outlined in FIG. 3 reveal thatinteraction region 71 is assumed rectangular, set P may hold threepoints described as the upper-left corner, the lower-left corner and theupper-right corner of a rectangular interaction structure 72. If,alternatively, the projection of computer screen interaction region 51is substantially rectangular, and this projected rectangle has the samecenter but is physically two times smaller than interaction structure72, the three points may be described as the upper-right corner, thelower-left corner and the lower-right corner of a rectangle that has thesame center but is two times smaller than interaction structure 72.Thus, by carefully choosing the points in set P together with theirdescription, any interaction structure 72 may be completely determined.

In addition to set P, a 3D point CA and another 3D point CB aredetermined at 90 a. These additional 3D points are determined so as tolie away from interaction region 71, that is, they lie at some distanceout of the plane that is closest to. or substantially containsinteraction region 71. The distance may be comparable to an edge ofprojection image 70. For example, point CA may be determined to lie nearprojection device 40 and point CB may be determined to lie at a distancefrom point CA that may be equal to the distance between projectiondevice 40 and projection surface 60 measured substantially parallel toprojection surface 60. Other choices for point CA and point CB may alsobe used. Additionally, sets A and B are generated during step 90 a. SetA includes a number n of lines A(i), each of which connects point CA toone of the points C(i) (0<i<n+1) in set P. Likewise, set B holds anumber n of lines B(i), each of which connects point Ca to one of thepoints C(i) (0<i<n+1) in set P. Finally, at 90 a, counters a, b are bothinitialized to the value of n.

Flow then continues on to step 90 b, where a decision is made whetherthe program elements outlined in FIG. 3 have revealed any information onthe 3D position and orientation of interaction structure 72. If thedecision is positive flow continues to step 90 c, where this informationis used to establish a priori relationships between the coordinates ofthe points in set P. For example, the steps outlined in FIG. 3 may haverevealed that interaction structure 72 is assumed to coincide with thex-z plane, in which case the a priori relationships may include therequirement that the y-coordinates of all points in set P are equal tozero. A pre-set library of a priori relationships may be provided to aidin the execution of this program element.

The program continues to 90 d, which may also be reached from gob if thedecision at gob is negative. At 90 d, line B(b) is removed from set B,after which counter b is decremented by 1.

The program continues to 90 e, where a decision is made whether complete3D information on the lines in sets A and B, together with a prioriinformation, constitutes enough information to uniquely determine thecoordinates of all the points in set P. For example, the programelements outlined in FIG. 3 may have determined that interaction region71 is assumed to be rectangular, but no information is known regardingits orientation or position. In this case set P may contain threepoints, corresponding to three corners of a rectangular interactionstructure 72. Each point C(i) (0<i<4) in set P would then be uniquelydetermined by the intersection of a line from set A and a line from setB if and only if sets A and B contained three lines each.

If the decision at 90 e is negative, the program continues to 90 f,where line B(b+1) is added once more to set B.

If the decision at 90 e is positive, program flow continues to 90 g. Theprogram flow may also continue from 90 f to 90 g. At 90 g a decision ismade whether counter b has reached zero, in which case the lines left inset B (which number may be equal to zero) are deemed necessary forunique determination of the coordinates of all the points in set P. Ifthe decision at 90 g is positive, program flow continues to 90 h. If thedecision at 90 g is negative, program flow reverts to god.

During 90 h, line A(a) is removed from set A, after which counter a isdecremented by 1. Program flow then continues to 90 i, where a decisionis made whether complete 3D information on the lines in sets A and B,together with the a priori information, constitute enough information touniquely determine the coordinates of all the points in set P.

If the decision at 90 i is negative, program flow continues to step 90j, where line A(a+1) is added once more to set A.

If the decision at 90 i is positive, program flow continues to step 90k. The program flow also continues from 90 j to 90 k. At 90 k, adecision is made whether counter a has reached zero, in which case thelines left in set A (which number may be equal to zero) are deemednecessary for unique determination of the coordinates of all the pointsin set P. If the decision at 90 k is negative, program flow reverts to90 h. If the decision at 90 k is positive, program flow continues to 90m, the details of which are described with reference to FIG. 5.

In FIG. 5, the program continues to 100 a, where counter p isinitialized to 1 and variable n is set to the number of points in set P.

Program flow then continues to 100 b where a decision is made whetherline A(p) (connecting point CA to point C(p) is included in set A. Ifthe decision is negative, program flow continues to 100 c, where counterp is incremented by 1.

If the decision at 10 Gb is positive, program flow continues to woe, atwhich the program identifies point C(p) to the user and then can querythe user to highlight this point using light-beam projection device 202,preferably from a position such as point CA, as determined previously at90 a (FIG. 4). The user can also be queried to affirm the highlightingaction by, for example, activating one of the buttons 203 a or 204 b, orthe like. The identification of point C(p) may occur, for example, byhaving the program display a visible screen mark 521 a-521 d at aposition on computer screen interaction region 51 associated with C(p),which may then be projected by projection device 40 to coincide withpoint C(p). Other means of identification are also possible, such as thecharacterization of point C(p) as ‘upper-right corner’ or the like.

Program flow then continues on to 100 f, where the program can waituntil the highlighting action is affirmed by the user, after which the3D orientation of the z′-axis and the 3D position of the z′=0 point (ofthe z′-axis) are measured with respect to the x y z coordinate system,using coordinate sensing device 201 and 301, and communicated to thecomputer using communication and control device 204 and/or 304. This 3Dorientation and position is then associated with line A(p) and stored inmemory. Program flow then continues to 100 c.

After 100 c program flow continues to 100 d where a decision is madewhether p is equal to n+1. If the decision is positive, it can beconcluded that all necessary data on lines A(p) have been ascertainedand program flow can continue to 100 g. If the decision at 100 d isnegative, program flow reverts to 100 b.

At 100 g a decision is made whether set B is empty. If the decision ispositive, it can be concluded that enough information to uniquelydetermine the 3D coordinates of all the points in set P is contained inthe a priori relationships combined with the available data on the linesin set A, and program flow continues to loop. If the decision at 100 gis negative, program flow continues to 100 h.

At 100 h counter p is again initialized to 1. The user is subsequentlyrequired to reposition the pointing device 20 to a different location,displacing it substantially parallel to projection region 60 over adistance substantially equal to the distance between projection region60 and his or her present location. Other locations may also be used.

Flow then continues to 100 i where a decision is made whether line B(p)(connecting point CB to point C(p)) is included in set B. If thedecision is negative, program flow continues to 100 j where counter p isincremented by 1.

If the decision at 100 i is positive, program flow continues to loom, atwhich point the program identifies point C(p) to the user and can querythe user to highlight this point using light-beam projection device 202.The program can also query the user to affirm the highlighting by, forexample, activating one of the buttons 203 a or 204 b or the like. Theidentification of point C(p) may occur, for example, by having theprogram display a visible screen mark 521 a, 521 b, . . . at a positionon computer screen interaction region 51 associated with C( ), which maythen be projected by projection device 40 to coincide with point C(p).Other means of identification are also possible, such as thecharacterization of point C(p) as ‘upper-right corner’ or the like.

Program flow then continues to loon, where the program may wait untilthe highlighting action is affirmed. After affirmation, the 3Dorientation of the z′-axis and the 3D position of the point z′=0 (of thez′-axis) are measured with respect to the x y z coordinate system, usingcoordinate sensing device 201 and 301, and are communicated to theprogram using communication and control device 204 and/or 304. The 3Dorientation and position are then associated with line B(p) and can bestored in memory. Program flow then continues to 100 j.

After 100 j program flow continues to look where a decision is madewhether p is equal to n+1. If the decision is positive, it is concludedthat all necessary data for lines B(P) has been ascertained and programflow continues to loop. If the decision is negative, program flowreverts to 100 i.

At 100 p it is concluded that the combined information of the a priorirelationships and the data for lines in sets A and B that is stored inmemory is enough to establish the coordinates of all points in P, as isfurther explained with reference to FIG. 6.

Referring to FIG. 6, as will be appreciated by those skilled in the art,at 110 a the available information contained in the a priorirelationships and the orientations and positions of the lines in sets Aand B may be used to establish the coordinates of each of the points inset P, all measured with respect to the x y z coordinate system. It mayhappen that the 3D data associated with lines A(p) and B(p) (1<p<n+1)cause them not to intersect at point C(p); for example, this could bethe case due to insufficient accuracy in determining the orientationsand positions of lines A(p) and B(p). Under such circumstances pointC(p) may be estimated or determined in such a way that it lies halfwayalong the shortest line-segment that connects lines A(p) and B(p). Othermethods for determining point C(p) are also possible.

Once the complete 3D description of interaction structure 72 has beenestablished (given the available data and assumptions), program flowcontinues to nob. At nob, a method M is constructed that maps points ofinteraction structure 72 to computer screen interaction region 51. Suchmethods are well known to those skilled in the art. For example, amethod such as that described in U.S. Pat. No. 6,373,961 to Richardsonet al. (2002) may be used, but other appropriate methods may also beused. For completeness, the method disclosed in the Richardson et al.'961 patent will briefly be explained here. Referring to FIG. 20,interaction structure 72 may be defined by line segments JK and ML.Furthermore, point F may define point-of-aim 210, which is also theintersection between the z′-axis and interaction structure 72. The linesegments JK and ML are generally not parallel. If not parallel, then theline segments JK, ML are extended until they meet at a point H. Then aline is drawn through F and H, that intersects segment JM at point P andsegment KL at point O. If the segments JK. and ML are parallel, the aline is drawn instead through F that is parallel to JK, and whichintersects the other two line segments as described. The processcontinues similarly with the other segments, which are extended to meetat point G. A line through F and G intersects segment JK at point R andsegment ML at point Q. Subsequently, the following distances aremeasured and noted as percentages: JR/JK, KO/KL, LQ/LM and MP/MJ. Thenfour points S, T, U, V are chosen as shown in FIG. 20, that form anexact rectangle STUV; this rectangle may define computer screeninteraction region 51. Further, points W, X, Y, Z are chosen on thesides of the rectangle STUV in such a way that SZ/ST=JR/JK, TW/TU=KOIKL,UX/UV=LQ/LM and VY/VS=MP/MJ. Then the points Z and X are joined by aline, and the points Y and W are joined by a line. The point of theintersection of these latter two lines is N, which is the point thatresults from the operation of method M.

Referring once again to FIG. 6, after nob, program flow continues to 110c where a decision is made whether the user has requested the program toend. If the decision is positive, the program ends at 110 k.

If the decision at 110 c is negative, program flow continues to 110 d,where a decision is made regarding whether the user has requested adirect-pointing action, such as activating button 203 a or 203 b or thelike.

If the decision at 110 d is negative, program flow continues to 110 e,where the light-beam projection device 202 can be instructed or causedto de-activate (using, for example, control device 204 and/or 304).Furthermore, a software routine (not shown) that controls computercursor 501 (see also FIG. 2) is instructed that the user does not wantto execute a direct-pointing action, after which program flow reverts to110 c. Such cursor control routines are well known to those skilled inthe art and are therefore not described here.

If the decision at 110 d is positive, program flow continues to 110 f,where a decision is made whether the z′-axis intersects interactionstructure 72. Those skilled in the art will appreciate that this ispossible because all relevant 3D information is known or is measurableby coordinate sensing device 201 and 301. If the decision is positive,program flow continues to 110 h, at which method M is used to map theintersection point of the z′-axis with interaction structure 72 tocomputer screen interaction region 51. This mapped position, as well asthe user's desire to execute a direct-pointing action, are communicatedto the cursor control routine (not shown) running on the computer.

After 110 h, program flow continues to 110 i where a decision is madewhether the user wishes to execute an action associated with theposition of cursor 501. For example, activating button 203 a or 203 b orthe like may indicate such a request. If the decision is negative,program flow reverts to 110 c.

If the decision at 110 i is positive, program flow continues to 110 j,where the cursor control routine (not shown) is requested to execute theintended action. Such an action may, for instance, be a ‘double-click’action or the like. Program flow then reverts to 110 c.

There may be situations for which the system of equations that allowsdetermination of all coordinates of the points in set P will be somewhatill-posed. This could for example occur if locations CA and CB arechosen too close together, or if the angles of some pointing lines 21with respect to interaction region 71 are too small, as will beappreciated by those skilled in the art. In such cases, the user may bedirected to choose a different point for locations CA and/or CB fromwhere the various points C(p) are to be highlighted.

Thus, methods and means are disclosed that afford a highly flexible andeasily deployable system for interacting with a presentation in adirect-pointing manner at a location not specifically designed oradapted for such a purpose. Moreover, although it is desirable to havehighly accurate coordinate sensing device 201 and 301, in some instancessuch may not be necessary because the visual feedback afforded by adisplayed cursor will compensate to a large extent for any errors madein the measurements of coordinate parameters. The same holds true forthe importance of any discrepancies between the actual shape ofinteraction region 71 and that of the interaction structure 72 that isassumed to coincide with it. Also, minor discrepancies between theactual position and orientation of interaction region 71 and the assumedposition and orientation of interaction structure 72 (which is assumedto coincide with interaction region 71) need not be of criticalimportance, as will be appreciated by those skilled in the art.

Mathematically, there are infinite possible shapes for interactionstructure 72 as well as infinite a priori relationships, sets P, A, Band methods M. To further explain the invention, what follows is a listof examples that are believed will be encountered most often. Theseexamples are not meant to restrict the scope of the present invention inany way, but merely serve as further clarification.

Referring to FIG. 7, it can be assumed that the venue where thepresentation is to be made is set up such that projection image 70 andinteraction region 71 are substantially rectangular. Such may be thecase when the optical axis of projection device 40 is substantiallyparallel to the normal to projection region 60. Projection region 60 maybe a projection screen on a stand, as shown, but may also be a wall orany other substantially vertical surface. It can also be assumed thatthe bottom and top edges of both projection image 70 and interactionregion 71 are substantially horizontal. Furthermore, it can be assumedthat interaction region 71 is substantially the same size as projectionimage 70 and that computer screen interaction region 51 is substantiallythe same size as computer screen image 50. Additionally, it can beassumed that calibration points 721 a, 721 d substantially coincide withthe projected versions of screen marks 521 a, 521 d. Finally, it isassumed that base station 30 is positioned such that the x-y plane issubstantially horizontal and the x-z-plane substantially coincides withthe plane of interaction region 71. To facilitate in the positioning ofbase station 30, the user may⋅be aided by level-sensing device 303 andvisible markings 302.

Referring to FIGS. 3 and 7, process elements 80 a-j may then result,either through default settings or through user-supplied settings, inthe assumptions that interaction structure 72 is a rectangle that liesin the x-z plane and that its top and bottom edges are parallel to thex-y plane.

Referring to FIGS. 4 and 7, program element 90 a may then result in aset P containing three points that define the upper-right corner C(i),the upper-left corner C(2) and the lower-left corner C(3) of interactionstructure 72. Additionally, program element 90 a may determine point CA(not denoted as such in FIG. 7) to lie away from projection region 60,for example at the center of one of the two instantiations of pointingdevice 20, as shown in FIG. 7. Point CB may be determined anywhere inspace. Program element 90 a may also result in sets A and B eachcontaining three lines, connecting the points in set P to points CA andCB respectively. Program element 90 c may then result in a priorirelationships such that all points in set P have y-coordinate equal tozero, that the upper-left corner will have an x-coordinate equal to thex-coordinate of the lower-left corner and that its z-coordinate will beequal to the z-coordinate of the upper-right corner. It will then beappreciated by those skilled in the art that this a priori information,together with complete 3D information on two lines in set A will besufficient to uniquely determine the position, size and orientation ofinteraction structure 72 with respect to the x y z coordinate system.Therefore, program elements god, 90 e, 90 f, 90 g may result in an emptyset B. Moreover, program elements 90 b, 90 i, 90 j, 90 k may result inthe removal from set A of line A(2), connecting point CA to point C(2).

Referring to FIGS. 5 and 7, program elements 100 a-p may result in theprogram identifying point C(1) by instructing the computer (not shown)and projection device 40 to project screen mark 521 a onto projectionregion 60, resulting in the appearance of calibration point 721 a.Subsequently, the user is required to use light-beam projection device202 to highlight calibration point 721 a and indicate the success ofthis action to the computer (not shown) by, for example, pressing button203 a. As a result, the orientation and position of the z′-axis areassumed to define line A(1). The same actions are then performed forpoint C(3) and line A(3). Since set B is empty, the user need not berequired to reposition pointing device 20. The two depictions ofpointing device 20 in FIG. 7 are meant to illustrate that pointingdevice 20 only needs to be redirected and not repositioned during thisexercise. It will be appreciated by those skilled in the art thatprogram element loop will then successfully result in a full 3Ddescription of the three points in set P.

Referring to FIGS. 6 and 7, program element 110 a may then result in thedescription of interaction structure 72 as a rectangle with upper-rightcorner C(I), upper-left corner C(2) and lower-left corner C(3). Step 110b may then result in a method M that maps a point δ (not shown) ininteraction structure 72 to a point c (not shown) in computer⋅screeninteraction region 51 in such a way that the ratio of distances betweenδ and any two of the four corners of interaction structure 72 is thesame as the ratio of distances between c and the two correspondingcorners of computer screen interaction region 51, as will be appreciatedby those skilled in the art. Steps 110 c-k may then result in a veryintuitive cursor control device that responds to a direct-pointingaction by deactivating light-beam projection device 202 and showingcursor 501 at substantially point-of-aim 210 of pointing device 20whenever point-of-aim 210 lies in projection image 70 (which in thisexample, by assumption, substantially coincides with interaction region71). Since there is no necessity for a computer generated cursor and alight spot to be visible simultaneously there will not be any cause forconfusion as to which of the two is the ‘actual cursor’. Cursor 501 maybe hidden from view when point-of-aim 210 does not lie in interactionstructure 72, in which case light-beam projection device 202 may beactivated automatically. Also, intuitive actions such as ‘double click’may be provided by steps 110 c-k.

Referring to FIG. 8, it can be assumed that the venue where thepresentation is to be given is set up such that projection image 70 andinteraction region 71 are substantially rectangular. Such may be thecase when the optical axis of projection device 40 is substantiallyparallel to the normal to projection region 60. Projection region 60 maybe a projection screen on a stand, as shown, but may also be a wall orany similar surface. Projection region 60 can be assumed to be orientedsubstantially vertically. It can also be assumed that the bottom and topedges of both projection image 70 and interaction region 71 aresubstantially horizontal. Furthermore, it can also be assumed thatinteraction region 71 is substantially the same size as projection image70 and that computer screen interaction region 51 is substantially thesame size as computer screen image 50. Additionally, it can be assumedthat calibration points 721 a, 721 c, 721 d substantially coincide withthe projected versions of screen marks 521 a, 521 c, 521 d. Finally, itcan be assumed that base station 30 is positioned such that thex-y-plane is substantially horizontal. No assumptions are made regardingthe x-z-plane and the y-z plane other than that they are substantiallyvertical. To facilitate in the positioning of base station 30, the usermay be aided by level-sensing device 303.

Referring to FIGS. 3 and 8, program elements 80 a-j may then result,either through default settings or user-supplied settings, in theassumptions that interaction structure 72 is a rectangle of which thetop and bottom edges are parallel to the x-y-plane (i.e., they arehorizontal) and the left and right edges are perpendicular to thex-y-plane (i.e., they are vertical).

Referring to FIGS. 4 and 8, program element 90 a may then result in aset P containing three points that define the upper-left corner C(1),the upper-right corner C(2) and the lower-left corner C(3) ofinteraction structure 72. Additionally, program element 9 oa maydetermine point CA (not denoted as such in FIG. 8) to lie away fromprojection region 60, for example, at the center of one of the threeinstantiations of pointing device 20, as shown in FIG. 8. Point CB (notdenoted as such in FIG. 8) may be determined to be displaced from pointCA in a direction substantially parallel to interaction region 71, overa distance that may be the same order of magnitude as the size ofinteraction region 71. Program element 90 a may also result in sets Aand B each containing three lines, connecting the points in set P topoints CA and CB respectively. Program element 90 c may then result in apriori relationships requiring that the upper-left corner will have x-and y-coordinates equal to the x- and y-coordinates of the lower-leftcorner and that its z-coordinate will be equal to the z-coordinate ofthe upper-right corner. As will be explained in detail below, the apriori information together with complete 3D information on two lines inset A and one line in set B will be enough to uniquely determine theposition, size and orientation of interaction structure 72 with respectto the x y z coordinate system. Therefore, program elements god, 90 e,90 f, 90 g may result in set B containing only line B(3). Moreover,program elements 90 h, 90 i, 90 j, 90 k may result in set A containingonly lines A(i) and A(2)

Referring to FIGS. 5 and 8, program elements 100 a-p may result in theprogram identifying point C(1), C(2) and C(3) by means of projectiondevice 40, in a manner similar to the one described in the previousexample. In this case, however, C(i) and C(2) may be highlighted fromapproximately the same location CA, but C(3) needs to be highlightedfrom a different location CB. To explain that the above-mentionedinformation is enough to uniquely establish the position, size andorientation of interaction structure 72, define the points in set P as:

$\begin{matrix}{{C(1)} = \begin{pmatrix}{x_{1} + {\lambda_{1} \cdot {Rx}_{1}}} \\{y_{1} + {\lambda_{1} \cdot {Ry}_{1}}} \\{z_{1} + {\lambda_{1} \cdot {Rz}_{1}}}\end{pmatrix}} & (1) \\{{C(2)} = \begin{pmatrix}{x_{1} + {\lambda_{2} \cdot {Rx}_{2}}} \\{y_{1} + {\lambda_{2} \cdot {Ry}_{2}}} \\{z_{1} + {\lambda_{2} \cdot {Rz}_{2}}}\end{pmatrix}} & (2) \\{{C(3)} = \begin{pmatrix}{x_{1} + {\lambda_{3} \cdot {Rx}_{3}}} \\{y_{1} + {\lambda_{3} \cdot {Ry}_{3}}} \\{z_{1} + {\lambda_{3} \cdot {Rz}_{3}}}\end{pmatrix}} & (3)\end{matrix}$

Here, points CA and CB are defined as (x1, y1, z1) and (x3, y3, z3)respectively. Moreover, lines A(1), A(2) and B(3) are defined as passingthrough CA, CA and CB respectively, lying in directions governed by(Rx1, Ry1, Rz1), (Rx2, Ry2, Rz2) and (Rx3, Ry3, Rz3). All of thesequantities are presumed to be measured by coordinate sensing device 201and 301. For a unique description of the points in set P a solution isrequired for λ1, λ2 and λ3.

Using these definitions the conditions described above can be writtenas:

$\begin{matrix}{{\begin{bmatrix}{Rz_{1}} & {{- R}z_{2}} & 0 \\{Rx_{1}} & 0 & {{- R}x_{3}} \\{Ry_{1}} & 0 & {{- R}y_{3}}\end{bmatrix}\begin{pmatrix}\lambda_{1} \\\lambda_{2} \\\lambda_{3}\end{pmatrix}} = \begin{pmatrix}0 \\{x_{3} - x_{1}} \\{y_{3} - y_{1}}\end{pmatrix}} & (4)\end{matrix}$

which can be solved in a straightforward manner according to theexpression:

$\begin{matrix}{\begin{pmatrix}\lambda_{1} \\\lambda_{2} \\\lambda_{3}\end{pmatrix} = \begin{pmatrix}{\lbrack {{{Rx}_{3} \cdot ( {y_{3} - y_{1}} )} + {{Ry}_{3} \cdot ( {x_{1} - x_{3}} )}} \rbrack/\lbrack {{{Rx}_{3} \cdot {Ry}_{1}} - {{Rx}_{1} \cdot {Ry}_{3}}} \rbrack} \\{\lbrack \frac{Rz_{1}}{Rz_{2}} \rbrack \cdot {\lbrack {{{Rx}_{3} \cdot ( {y_{3} - y_{1}} )} + {{Ry}_{3} \cdot ( {x_{1} - x_{3}} )}} \rbrack/\lbrack {{{Rx}_{3} \cdot {Ry}_{1}} - {{Rx}_{1} \cdot {Ry}_{3}}} \rbrack}} \\{\lbrack {{{Rx}_{1} \cdot ( {y_{3} - y_{1}} )} + {{Ry}_{1} \cdot ( {x_{1} - x_{3}} )}} \rbrack/\lbrack {{{Rx}_{3} \cdot {Ry}_{1}} - {{Rx}_{1} \cdot {Ry}_{3}}} \rbrack}\end{pmatrix}} & (5)\end{matrix}$

Note that this solution shows that, if point C(3) was highlighted fromany point on the pointing line 21 that is used to highlight point C(1),i.e.,

$\begin{matrix}{\begin{pmatrix}x_{3} \\y_{3} \\z_{3}\end{pmatrix} = \begin{pmatrix}{x_{1} + {\tau \cdot {Rx}_{1}}} \\{y_{1} + {{\tau \cdot R}y_{1}}} \\{z_{1} + {{\tau \cdot R}z_{1}}}\end{pmatrix}} & (6)\end{matrix}$

the solution for the three unknown λ's would collapse to

$\begin{matrix}{\begin{pmatrix}\lambda_{1} \\\lambda_{2} \\\lambda_{3}\end{pmatrix} = \begin{pmatrix}\tau \\{{\tau R}{z_{1}/{Rz}_{2}}} \\0\end{pmatrix}} & (7)\end{matrix}$

making unique determination of interaction structure 72 impossible.Conversely, the fact that points C(i) and C(2) are, in this example,both highlighted from substantially the same point CA does not cause anyproblems. It will be appreciated by those skilled in the art that C(i)and C(2) may also be highlighted from different points, without loss offunctionality.

Referring to FIGS. 6 and 8, the course and results of program elements110 a-k will be similar to those described in Example 1.

Referring to FIG. 9, in another example, the only assumptions made arethat interaction region 71 is substantially the same size as projectionimage 70, computer screen interaction region 51 is substantially thesame size as computer screen image 50, calibration points 721 a, 721 b,721 c, 721 d substantially coincide with the projected versions ofscreen marks 521 a, 521 b, 521 c and 521 d and computer screeninteraction region 51 is substantially rectangular. This situation mayarise when the optical axis of projection device 40 is not aligned withthe normal to projection surface 60.

Referring to FIGS. 3 and 9, program elements 80 a-j may then result,either through default settings or user supplied settings, in theassumption that interaction structure 72 is a quadrangle; no assumptionsare made regarding its position or orientation.

Referring to FIGS. 4 and 9, program elements 90 a may then result in aset P containing four points that define the upper-right, upper-left,lower-right and lower-left corners of interaction structure 72.Additionally, program element 90 a may conceive point CA (not denoted assuch in FIG. 9) to lie away from projection region 60, for example atthe center of the first of the two instantiations of pointing device 20,as shown in FIG. 9. Point CB may, for example, be determined to lie atthe center of the second of the two instantiations of pointing device20, as drawn in FIG. 9. Now, program elements god, 90 e, 90 f, 90 g andsteps 90 h, 90 i, 90 j, 90 k may result in sets A and B each containing4 lines.

Referring to FIGS. 5 and 9, program elements 100 a-p may result in theprogram identifying the four points in set P by means of projectiondevice 40, in a manner similar to the one described in Example 1. Inthis case, however, all four points in set P may be highlighted fromapproximately the same location CA first, after which all four pointsmay be highlighted from approximately the same location CB. Note thatFIG. 9, for reasons of clarity, only depicts the highlighting ofcalibration point 721 a. Each point C(i) may then be constructed as thepoint lying halfway the shortest line segment connecting lines A(i) andB(i); this line segment may have zero length.

Referring to FIGS. 6 and 9, the course and results of program elements110 a-k will be similar to those described with respect to the firstexample, with the exception of program element 110 b, the mappingelement. Now, a more elaborate method M is needed than the one describedin previous examples. For example, a method such as described in U.S.Pat. No. 6,373,961 to Richardson (2002) may be utilized, but otherappropriate methods may also be used.

A second embodiment will now be made with reference to FIG. 10, whichshows pointing device 20 and base station 30. Here, in addition to anyor all of the elements mentioned in the previous embodiment, pointingdevice 20 is also provided with distance measuring device 206, theposition and orientation of which with respect to the x′y′z′ coordinatesystem may be ascertained at the place of manufacture thereof and willbe presumed to be known. Distance measuring device 206 may for examplebe embodied by a focus adjustment, or optical sensor. A digital cameramay also be used. Distance measuring device 206 may determine thepoint-of-aim-distance 211 between the origin of the x′y′z′ coordinatesystem and the point-of-aim, measured substantially parallel to thez′-axis (see also FIG. 2). The point of aim 210 may lie on projectionregion 60, on which interaction region 71 may lie. Distance measuringdevice 206 may have associated with it a manual focus adjustment thatmay be adjusted by the user (manual focus adjustment not shown).Alternatively, distance measuring device 206 may comprise a circuit (notshown) that automatically determines the point-of-aim-distance 211between the origin of the x′y′z′ coordinate system and the point-of-aim.For example, if the point-of-aim lies on projection region 60, distancemeasuring device 206 may bounce light off of projection region 60. Indoing so, use may for instance be made of light-beam projection device202. Any other appropriate mechanism for determining distance may alsobe used for distance measuring device 206. The optical axes oflight-beam projection device 202 and distance measuring device 206 maycoincide, for instance by making use of partially-reflecting elements(not shown) such as disclosed in U.S. Pat. No. 4,768,028 to Blackie(1988).

The operation of the present embodiment will now be described withreference to FIGS. 2, 10, and 3. The process elements in FIG. 3 will beidentical to the ones described in the first embodiment, resulting insimilar assumptions regarding the shape of interaction region 71 (andinteraction structure 72) and possibly orientation and position ofinteraction structure 72.

Referring to FIG. 11, instead of the program elements described abovewith reference to FIG. 4, program flow now continues at 120 a. Programelements 120 a-120 h are shown to be similar to program elements 90 a-90m (FIG. 4), except that only point CA, set A and counter a areconsidered. That is to say, in the present embodiment it is no longernecessary to determine the second point CB and associated repositioningof pointing device 20 during the calibration procedure.

After program element 120 h, program flow continues with programelements outlined in FIG. 12. Referring to FIG. 12, program elements 130a-130 g are seen to be similar to steps 100 a-100 p (FIG. 5). Comparingprogram element 130 f with program element roof (FIG. 5), it can be seenthat at 130 f the program also stores information on thepoint-of-aim-distance (211 in FIG. 2) between the origin of the x′y′z′coordinate system and point C(p). Comparing elements 130 g and 100 p(FIG. 5), it can be seen that these point-of-aim-distances (211 in FIG.2) are also used in determining the 3D coordinates of the points in setP.

With complete information on the 3D coordinates of the points in set P,it is then possible to construct a 3D description of interactionstructure 72 (in FIG. 2). Therefore, program elements 110 a-110 k asdescribed above with reference to FIG. 6 may also be followed in thepresent embodiment.

Thus, methods and means are disclosed that afford a highly flexible andeasily deployable system for interacting with a presentation in adirect-pointing manner at a location not specifically equipped for sucha purpose. Moreover, when utilizing the second preferred embodiment itis often sufficient for the user to highlight various calibration points721 a, 721 b, . . . from one and the same position, making thecalibration procedure even more easy to follow.

Another embodiment will now be explained with reference to FIG. 13. FIG.13 shows another embodiment of the pointing device 20. Pointing device20 may be equipped with any or all of the elements mentioned in theother embodiments, such as described above with reference to FIG. 1 andFIG. 10. The present embodiment may include a base station 30 that hasassociated with it a coordinate system x y z. However, in the presentembodiment it can be assumed that the position of pointing device 20will remain substantially unchanged relative to interaction region 71over an extended period of time, and that the origin of coordinatesystem x y z may be assumed to be virtually anywhere instead of beingrelated to the base station 30. Furthermore, if any of the axes of the xy z system are chosen to be related to locally well-established,independent and stationary directions such as, for example, the Earth'smagnetic field and/or the Earth's gravitational field, the Earth itselfmay be interpreted as embodying base station 30. Under suchcircumstances there may not be a need for an artificial base station 30;coordinate sensing device 201 may then, for example, be embodied bydevices sensing the directions of the Earth magnetic and gravitationalfields, such as accelerometers and a compass (for example, model no.HMR3300 device as manufactured by Honeywell International Inc.,Morristown, N.J.), and communication and control device 204 may beconfigured to communicate directly with the computer (not shown).

The operation of the present embodiment will now be described withreference to FIGS. 8, 13, and 3. The remainder of the description of thepresent embodiment will, for purposes of explanation, include theassumption that any separately embodied base station 30 (FIGS. 8 and 13)is omitted entirely. It is also assumed that one of the axes of theorthogonal coordinate system x y z is substantially parallel to theEarth's gravity field (or has a defined relationship thereto), while thesecond and third axes of the coordinate system are in a fixed, knownrelationship to the at least one geographically defined axis. In thepresent embodiment it is assumed that the relative position of pointingdevice 20 with respect to interaction region 71 remains substantiallyunchanged, therefore the origin of coordinate system x y z will, forpurposes of explanation, be chosen to coincide with a fixed point in thepointing device 20. For the purpose of the present embodiment, it shouldbe understood that the three instantiations of pointing device 20 asshown in FIG. 8 substantially coincide.

It can be assumed in the present embodiment that a display system isarranged at the venue where a presentation is to be made, as acombination of a portable projection device 40 and projection surface60, for example a wall. It will furthermore be assumed that this displaysystem is connected, using appropriate means, to the computer (notshown) that generates the image.

Upon arriving at the venue, the user connects pointing device 20 to thecomputer (not shown), for example via a USB connection (not shown), orusing a wireless relay device (not shown). Also, the computer mayrecognize the connection and start a program, part of which may becontained in communication and control device 204 or in control logiccontained in the wireless relay device itself (not shown).Alternatively, the user may be required to load the program into thecomputer manually via a CD drive, a floppy drive, memory stick or thelike (not shown). In any case, the program may initiate a calibrationroutine that has as its object establishing the shape, position, sizeand orientation of a well-defined interaction structure 72, relative tothe x y z coordinate system, wherein the interaction structure 72 isassumed to substantially coincide with a scaled and parallel version ofinteraction region 71. The flow of this program will be explained withreference to FIG. 3.

At 80 a the program is initiated. At Bob defaults are entered forinteraction region 71. Specifically, interaction region 71 is assumed tobe a substantially parallel and scaled version of a well-definedinteraction structure 72. Moreover, the respective corners ofinteraction region 71 and interaction structure 72 are assumed tosubstantially lie on lines intersecting each other in the origin ofcoordinate system x y z. It should be noted that FIG. 8 shows aninteraction region 71 and an interaction structure 72 that are almostcoincident, but this is only meant for illustrative purposes and is nota limitation on the scope of the invention. Again referring to FIG. 3,at Bob default values are also established for the orientation andposition of the interaction structure 72. For example, the defaultvalues may provide that interaction region 71 is substantially aparallel and scaled version of an interaction structure 72 that is aflat rectangle of which the two most vertical sides are substantiallyparallel to the Earth's gravitational field, and of which the two mosthorizontal sides are substantially perpendicular to the Earth'sgravitational field; moreover, the default values may provide that therespective corners of interaction region 71 and interaction structure 72substantially lie on lines intersecting each other in the origin ofcoordinate system x y z. The default values may furthermore provide thatthe position of interaction structure 72 is such that the distancebetween pointing device 20 and the lower left corner of interactionstructure 72 is equal to 1. Note that other values for the foregoingdistance may be equally valid in the present embodiment. Based on theforegoing default values, calibration points 721 a, 721 c, 721 d, . . .can define characteristic features of interaction region 71 and can alsodefine characteristic features of interaction structure 72.

At 80 c a decision is made whether the default values for interactionregion 71 and interaction structure 72 should be accepted or overriddenby the user. If the default values are to be accepted, the program flowcontinues to 80 j, the details of which are explained below withreference to FIG. 1i . If the defaults are to be overridden, the programflow continues with elements 80 d-80 i, during which the user mayoverride any of the default settings. The user may be aided duringprogram elements 80 d-80 i by a library of predetermined shapes,predetermined orientations and/or predetermined positions.Alternatively, the user can be provided with the capability to constructcustom shapes, orientations and/or positions. In any event, program flowcontinues to 80 j.

Referring to FIG. 11, program flow now continues to 120 a. Programelements 120 a-120 h are substantially similar to program elements 90a-90 m (FIG. 4), except that only point CA, set A and counter a⋅⋅areconsidered. In the present embodiment it is not required to determine asecond point CB and an associated repositioning of pointing device 20during the calibration procedure.

After 120 h, program flow continues with elements described withreference to FIG. 14. In FIG. 14, program elements 140 a-140 g are shownto be similar to steps 130 a-130 g (FIG. 12). Comparing element 140 fwith element B of (FIG. 12), it can be seen that element 140 f does notinclude storing information for any directly measured distance. Element140 f need not include storing information on the position of thez′-axis, because the position of pointing device 20 is assumed to remainsubstantially unchanged over an extended period of time. Comparingelements 140 g and BOg, it can be seen that any directly measureddistance is not needed to determine the 3D coordinates of the points inset P (see FIG. 4). In fact, having the default distance (set to 1)between pointing device 20 and the lower left corner of interactionstructure 72 is sufficient for operation of the system in the presentembodiment. To explain this fact, reference is again made to FIG. 8.Using the above default values, interaction structure 72 will becompletely defined by, for example, its upper-left corner C(i), itsupper-right corner C(2) and its lower-left corner C(3)

$\begin{matrix}{{C(1)} = {\lambda_{1} \cdot \begin{pmatrix}{Rx_{1}} \\{Ry_{1}} \\{Rz_{1}}\end{pmatrix}}} & (8) \\{{C(2)} = {\lambda_{2} \cdot \begin{pmatrix}{Rx_{2}} \\{Ry_{2}} \\{Rz_{2}}\end{pmatrix}}} & (9) \\{{C(3)} = {\lambda_{3} \cdot \begin{pmatrix}{Rx_{3}} \\{Ry_{3}} \\{Rz_{3}}\end{pmatrix}}} & (10)\end{matrix}$

lying on lines A(1), A(2) and A(3) that connect the origin to points(Rx1, Ry1, Rz1), (Rx2, Rye, Rz2) and (Rx3, Ry3, Rz3) respectively. Usingthese definitions, the conditions described above determinerelationships between the various variables that can be written as

$\begin{matrix}{{\begin{bmatrix}{Rz_{1}} & {{- R}z_{2}} & 0 \\{Rx_{1}} & 0 & {{- R}x_{3}} \\{Ry_{1}} & 0 & {{- R}y_{3}}\end{bmatrix}\begin{pmatrix}\lambda_{1} \\\lambda_{2} \\\lambda_{3}\end{pmatrix}} = \begin{pmatrix}0 \\0 \\0\end{pmatrix}} & (12)\end{matrix}$

which will have non-trivial solutions only if the determinant of thematrix equals zero. Then, it can be shown that any combination of (λ1,λ2, λ3) that can be written in the form:

$\begin{matrix}{\begin{pmatrix}\lambda_{1} \\\lambda_{2} \\\lambda_{3}\end{pmatrix} = {\begin{pmatrix}{{Rz}_{2}/{Rz}_{1}} \\1 \\{( {R{z_{2} \cdot R}x_{1}} )/( {R{z_{1} \cdot R}x_{3}} )}\end{pmatrix} \cdot \alpha}} & (13)\end{matrix}$

where α is any arbitrary real number, will generate solutions forinteraction structure 72 that are parallel to each other. The assumptionthat the distance between pointing device 20 and the lower left cornerof interaction structure 72 is 1 will hence uniquely generate one ofthese solutions. To see that other assumptions regarding this distancedo not influence the operation of the present embodiment, reference ismade to FIG. 15. In FIG. 15, projections of two parallel solutions forinteraction structure 72 are shown, obtained for different values ofdistances CA-C(3). When it is assumed, for purposes of explanation, thatthese two solutions are parallel to the z-x plane, FIG. 15 may beinterpreted as a projection of the two solutions onto the x-y plane.These projections are shown as the thick line segments C(3)-C(2) andCC3-CC2. FIG. 15 also shows the projection of point CA (i.e., the originof coordinate system x y z), from where the lower left and upper rightcorners of interaction structure 72 were highlighted, and line-segmentsC(3)-CA and C(2)-CA which coincide with the (projections of) thehighlighting lines A(3) and A(2) (not denoted as such in FIG. 15).Finally, line-segment BB1-CA indicates (the projection of) a pointingline that is consistent with a point-of-aim BB1 on the one andpoint-of-aim BB2 on the other of the two solutions for interactionstructure 72. To show that BB1 and BB2 represent the same horizontalcoordinate when measured relative to the appropriate solution forinteraction structure 72, the lengths of line segments C(3)-BB1,C(2)-BB1, CC3-BB2, CC2-BB2, BB1-CA and BB2-CA are represented by bb1,bb1, b1, b2, aa12 and a12, respectively. It is sufficient to show thatbb1/bb1=b1/b2. Consider the following equalities:

$\begin{matrix}{\frac{{bb}\; 1}{\sin\beta 1} = \frac{{aa}\; 12}{\sin\alpha 1}} & (14) \\{\frac{{bb}\; 2}{\sin\;\beta\; 2} = \frac{{aa}\; 12}{\sin\;\alpha\; 2}} & (15)\end{matrix}$

while, at the same time

$\begin{matrix}{\frac{b\; 1}{\sin\beta 1} = \frac{a\; 12}{\sin\alpha 1}} & (16) \\{\frac{b\; 2}{\sin\;\beta\; 2} = \frac{a\; 12}{\sin\;\alpha\; 2}} & (17)\end{matrix}$

From this it follows that

$\begin{matrix}{\frac{{aa}\; 12}{{bb}\; 1} = \frac{a\; 12}{b\; 1}} & (18) \\{\frac{{aa}\; 12}{{bb}\; 2} = \frac{a\; 12}{b\; 2}} & (19)\end{matrix}$

which, in turn, provides that

$\begin{matrix}{{bb1\frac{a12}{b1}} = { {bb2\frac{a12}{b2}}\Rightarrow\frac{bb1}{bb2}  = \frac{b1}{b2}}} & (20)\end{matrix}$

This implies that BB1 and BB2 represent the same horizontal coordinatewhen measured relative to the appropriate solution for interactionstructure 72. Note that, if FIG. 15 is interpreted as a projection ontothe z-y-plane, it can be concluded that BB1 and BB2 also represent thesame vertical coordinate when measured relative to the appropriatesolution of interaction structure 72. Therefore the initial assumptionthat the distance between C(3) and CA is equal to 1 does not influencethe operation of the third preferred embodiment.

It is theoretically possible that there are no non-zero solutions forthe parameters λ1, λ2 and λ3 when the determinant referred to above inequation (12) is non-zero. Such may be the case, for example, due toerrors in measurements or in the assumed rectangular shape ofinteraction region 71. In such cases additional techniques may be usedto find an acceptable solution for interaction structure 72. Forexample, a minimization routine may be used to find a solution forinteraction structure 72 that minimizes a summation of the distancesbetween some of its corners (which, by assumption, lie on linesconnecting the origin of coordinate system x y z with the corners ofinteraction region 71) and the highlighting lines.

With complete information on the 3D coordinates of C(i), C(2) and C(3)it is possible to construct a 3D description of interaction structure72. Therefore, program elements 110 a-110 k as described in the firstembodiment and explained above with reference to FIG. 6 may also befollowed in the present embodiment.

There may be situations in which the user is not able to hold pointingdevice 20 continuously at precisely the same position while performingthe actions required by the calibration procedure described in FIGS. 3,11 and 14, or during the use of the system as a direct-pointing device.Such changes in position of the pointing device 20 can cause errors inthe calculation of the point-of-aim. It will be appreciated that if thediscrepancy between the calculated and the true point-of-aim is smallenough, the visual feedback provided by the displayed cursor (501 inFIG. 1) during use of the system as a direct-pointing device will stillafford the user the perception that direct-pointing is being performed.

There are many other methods capable of establishing position, size andorientation of interaction structure 72, as will be appreciated by thoseskilled in the art. For example, if the distance between pointing device20 and interaction structure 72 is presumed known, if interactionstructure 72 is assumed to be rectangular with two vertical and twohorizontal sides and if its aspect ratio (the ratio between itshorizontal size and its vertical size) is also presumed known, thenknowledge of two lines from CA to the upper-right and lower-left corneris sufficient to narrow the number of solutions for interactionstructure 72 down to 2, dictated by 2 solutions of a quadratic equation.One further assumption is then required to determine which of these 2solutions is the correct one; this assumption may be in the form of athird line passing through yet another characteristic point ofinteraction structure 72, but it may also be in the form of knowledge ofthe (approximate) angle between the plane in which interaction structure72 lies and a line connecting the origin to one of its corners. Otherscenarios may also be conceived for which solutions may be devised thatare within the scope of the general methods set forth herein.

In the present embodiment, using well-established and stationarydirections such as, for example, the Earth's magnetic field and theEarth's gravitational field, it may be possible to omit a separatelyembodied base station, making the present embodiment of the systempossibly more compact, less expensive to make and easier to deploy.

Another embodiment of a system according to the invention will now bedescribed with reference to FIG. 16. In the present embodiment ahandheld presentation device 25 contains a power source 205,communication and control device 204 and a directional sound recordingdevice 251. The sensitivity region of the directional sound recordingdevice 251 may be substantially oriented along the long axis ofpresentation device 25. Any or all of the features contained in pointingdevice 20, already described in previous embodiments or to-be-describedin the additional embodiments, may also be contained in presentationdevice 25; any or all of features 201-207 are collectively depicted asmodule 200. In the same way, the fourth preferred embodiment also maybut need not provide base station 30 and its associated elements, suchas elements 301-305 or a wireless relay device (not shown in FIG. 16).

The directional sound recording device 251 may be provided withso-called zoom capabilities, such as those afforded by, for example, theECM-Z60 Super Zoom Microphone as manufactured by Sony. Alternatively,directional sound recording device 251 may comprise multiple directionalmicrophones (not shown) with different sensitivity regions, so that zoom‘capabilities may be emulated. In these cases, presentation device 25may also be provided with zoom control device 252, capable of adjustingthe sensitive volume of directional sound recording device 251 either bymanual control or automatically. Directional sound recording device 251may communicate with the computer (not shown) and/or base station 30(not shown in FIG. 16) through communication and control device 204and/or 304 (not shown in FIG. 16). A control program described in FIG.17 may be transferred to the computer (not shown) or be incorporated incommunication and control device 204 and/or 304. Moreover, there may beprovided a storage medium for storage of sound data (not shown) in oneof the components of the described system, as well as means to play backsound, such as a loudspeaker (not shown).

During a presentation it may occur that a member of the audience wishesto communicate verbally with the presenter (user). Often, the acousticsof the room preclude other members of the audience from hearing suchcommunication. In such cases, the user may point presentation device 25in the direction of the member of the audience who wishes to communicatewith the user. The user may then activate directional sound recordingdevice 251 by activating controls such as button 203 a or zoom controldevice 252. The latter may also be used to acoustically zoom in on theparticular member of the⋅audience. Directional sound recording device251 may then communicate with the computer (not shown) and record thecommunication, for example, in computer memory (not shown). At the sameor later time the user may request the recording to be played back, forinstance over speakers (not shown) driven by the computer (not shown),by activating controls such as button 203 b. The computer program may beconfigured such that one and the same command from the user, such as theactivation of button 203 a or zoom control device 252, initiatessubstantially simultaneous recording and playback. Measures tocounteract any acoustical interference when playback and recording occuralmost simultaneously may be implemented as well. Such measures are wellknown in the art.

Referring to FIG. 17, to facilitate the recording and playback ofsounds, general elements, 150 a-150 q of a program are shown. Theseprogram elements may be executed by the computer (not shown), and may beloaded into the computer by such means as floppy discs, memory sticks orCDs (not shown). The programs may be pre-loaded in base station 30, itsassociated wireless relay device (both not shown in FIG. 16) orpresentation device 25, and transferred by means of a USB port or thelike (not shown) upon connecting any of these components to the computer(not shown).

At 150 a the program is initialized, old recordings are erased and arecord-flag and a playback-flag are unset; this indicates that bothrecording and playback are not activated.

Program flow continues to 150 b, where a decision is made whether theuser requests the program to end. Buttons (203 a, 203 b in FIG. 16) orthe like may be used for this purpose.

If the decision at 150 b is positive, program flow continues to 150 q,where any recording or playback is stopped, playback and record flagsare unset, old recordings are erased and the program ends. If thedecision at 150 b is positive, program flow continues to 150 c.

At 150 c a decision is made whether the user has requested soundrecording. If the decision is positive, program flow continues to 150 d.If the' decision is negative, program flow continues on to 150 f.

At 150 d a decision is made whether the record-flag is unset, indicatingthat recording is not already in progress. If the decision is negative,program flow continues to 150 f. If the decision is positive, programflow continues to 150 e, where the record flag is set, any oldrecordings are erased and sound recording is started, after which theprogram flow continues to 150 f.

At 150 f, a decision is made whether the user has requested soundplayback. If this decision is positive, program flow continues to 150 g.If the decision is negative, program flow continues to 150 i.

At 150 g a decision is made regarding whether the playback flag isunset, indicating that playback is not already in progress. If thedecision is negative, program flow continues to 150 i. If the decisionis positive, and there is some sound data to be played back, programflow continues to 150 h, where the playback flag is set and soundplayback is started, after which the program flow continues to 150 i.

At 150 i a decision is made whether the user has requested that soundrecording is to be terminated. If the decision is positive, program flowcontinues to 150 j. If the decision is negative, program flow continueson to step 150 m.

At 150 j a decision is made whether the record-flag has been set,indicating that recording is in progress. If the decision is negative,program flow continues to 150 m. If the decision is positive, programflow continues to 150 k, where the record flag is unset and soundrecording is stopped, after which the program flow continues to 150 m.

At 150 m a decision is made whether the user has requested that soundplayback is to be terminated. If the decision is positive, or if the endof the recorded sound has been reached, program flow continues to 150 n.If the decision is negative, program flow reverts to step 150 b.

At ion a decision is made whether the playback flag has been set,indicating that playback is in progress. If the decision is negative,program flow reverts to 150 b. If the decision is positive, program flowcontinues to 150 p, where the playback flag is unset and sound playbackis stopped, after which the program flow reverts to 150 b.

Thus, methods and means are disclosed that afford a user the capabilityto easily capture and playback comments made by a member of theaudience, even in the presence of substantial background noise.

While the above description contains many specificities, these shouldnot be construed as limitations on the scope of the invention, Manyother variations are possible. For example, presentation device 25 orpointing device 20 may be hand held, but may also be carried by the userin a different manner, such as by means of a headset, finger worn ringor the like.

Although the first, second and third embodiments make use of theassumption that the interaction structure 72 and interaction region 71are quadrangles, this need not be the case even when the correspondingcomputer screen interaction region 51 is rectangular in shape. Forexample, projection region 60 may be spherical in shape. This may causethe projection of a square computer screen interaction region 51 toresult in interaction region 71 having the general shape of asphere-segment. Other shapes are also possible, depending on a number offactors such as the angle between the optical axis of projection device40 and projection region 60. It will be appreciated by those skilled inthe art that set P (see FIG. 4, step 90 a and FIG. 11, step 120 a) andmethod M (see FIG. 6, step nob) may become more complicated under thesecircumstances, but may still be well defined. In fact, method M and setsP, A, B may be constructed in any way that is advantageous to theparticular system application. It is also possible to determine morepoints and associated line sets than just CA and CB, and associated linesets A and B. Specifically, set P may have more or fewer than the numberof points described with reference to the foregoing embodiments,depending on the complexity of the presentation venue. Also, sets A andB may contain more lines than the minimum number needed to establish thecoordinates of the points in set P.

The present invention may make use of mathematical techniques notdescribed explicitly herein but well known to those skilled in the artto aid with various aspects of the present invention, for example in thedetermination of position and/or orientation of interaction structure72. The second example of the first embodiment, for example, wasdescribed as relying on three lines highlighting corners of theinteraction structure 72. It is also possible that a more accuratesolution for the position and/or orientation of interaction structure 72may be obtained when the user is requested to also highlight the fourthcorner of the screen. An appropriate minimization routine may then beused to find a solution characterized by, for example, a minimumaccumulated distance between the four corners of interaction structure72 and the closest highlighting line.

Moreover, although set P is described as containing points that areneeded to completely define interaction structure 72, other embodimentsof the invention may use so-called “control points” for quality controlpurposes. Such control points may be used to test the validity of theassumptions made concerning, for example, the shape, the position, sizeand/or orientation of interaction region 71 and, therefore, interactionstructure 72, as well as to test the accuracy of the measurements madeto establish the 3D features of the various lines. As an example,consider the case in which interaction structure 72 is taken to be arectangle for which all data needed to uniquely establish its size,orientation and position with respect to the x y z coordinate system hasbeen ascertained by the program elements described with respect to theforegoing embodiments. Moreover, in this example interaction region 71and, therefore, interaction structure 72, are assumed to substantiallycoincide with the projection of a rectangular computer screeninteraction region 51. Then, the computer may display a suitable screenmark 521 a, 521 b, . . . at, for example, the center of computer screeninteraction region 51, which may be projected by projection device 40onto projection region 60. It will be appreciated that the processelements described herein may be used to calculate 3D coordinates ofthis projected point, based on the available data regarding shape, size,orientation and position of interaction structure 72. The user may thenbe required to highlight the projected point using light-beam projectiondevice 202 and indicate the success of this action to the computer by,for example, activating button 203 a. If all measurements andhighlighting actions were accurate enough and no false assumptions weremade, the 3D coordinates of the projected point should substantiallyconform to the 3D characteristics of the z′-axis. If the discrepancy isdeemed too large the user may be required to repeat part or all of thecalibration steps outlined in the present invention.

There may also be more than one method M and sets P, A and B, each ofwhich may be associated with a different interaction structure 72 andinteraction region 71. There may be more than one interaction structure72 and interaction region 71, each of which may, but need not, lie onprojection region 60 and each of which may, but need not, be associatedby means of projecting screen marks 521 a, 521 b, . . . , with one ormore computer screen interaction regions 51.

Although coordinate sensing device (201 and 301 in FIG. 1.) were in someembodiments described as being able to provide information on the 3Dposition and 3D orientation of pointing device (20 in FIG. 2) relativeto the x y z coordinate system, it should be understood that suchinformation provision requirements may be relaxed under somecircumstances. Specifically, in the first embodiment it is only requiredthat the 3D position and 3D orientation of pointing line (21 in FIG. 2)to be known, instead of having complete information on the position ofpointing device (20 in FIG. 2) along the pointing line. That is, in somecases pointing device may be moved along pointing line without loss offunctionality. In such embodiments the coordinate sensing devices needonly provide information on the 3D position and 3D orientation of a line(as opposed to a line-segment) substantially intersecting pointingdevice. If coordinate sensing devices are able to provide complete 3Dinformation (i.e., 3D position and 3D orientation) of pointing device,as opposed to pointing line, the extra positional information may, forexample, be used to implement the capability to zoom in on a regionaround point-of-aim (210 in FIG. 2); other actions may also be based onthe extra positional information. The foregoing capability may beinferred from the description of the third embodiment, in which thecoordinate sensing device only is used to provide information on theangle between the pointing line and two other fixed lines, instead offull position and orientation information about a line segment.

Although the first, second and third embodiments describe theapplication of the invention as a cursor control device, the inventionmay also be used to facilitate non-cursor-related applications. Suchapplications may include “virtual writing” on the interaction region 71,target practice and the like. Also, the invention may be used other thanfor presentations. For example, methods of the invention may be employedto control a cursor on a television screen in order to make selectionsfrom menus associated with such things as Digital Satellite Television;other applications may also be anticipated.

Moreover, the features of the present invention that enable the trackingof point-of-aim relative to an interaction region may be enhanced byalgorithms that allow the filtering of involuntary, fast and/or smallhand-movements (that may be caused, for example, by the activation ofbuttons). Such algorithms may be used to control a point that moves lesserratically than the actual point-of-aim while still being associatedwith it. Such motion filtering may produce a more steady motion ofcursor 501. Such algorithms may also be used when the user is requiredto highlight calibration points 721 a, 721 b, . . . . Filter algorithmsare well-known in the art.

The present invention also contemplates the inclusion into pointingdevice 20 or presentation device 25 of sensors capable of detectingmotion or acceleration, both linear and angular, in addition to or aspart of coordinate sensing device 201. Such sensors may be used todetect unintended motion or acceleration of pointing device 20 orpresentation device 25 that may be caused, for example, by trembling ofthe user's hand. The programs described above with reference to FIGS. 5,6, 12 and 14 may be enhanced by algorithms that compare the output ofsuch sensors and/or coordinate sensing device to predefined thresholds,so that a change in measured orientation and/or position by coordinatesensing device 201 may be recognized as significant only if such outputexceeds these thresholds. Using threshold selection, a change in cursorposition may only be affected if inferred to be intentional, avoidingthe type of “jitter” associated with the use of regular laser pointersby a user with an unsteady hand.

Furthermore, pointing device 20 may be equipped with an image capturingdevice, such as a digital camera, preferably with zoom and controllablefocus capabilities. Other image capturing devices, in combination withappropriate optical devices, may also be used. As stated before, such adigital camera may be used as an embodiment of distance measuring device206. Referring to FIG. 18, such a digital camera or the like (not shown)may also be used to aid in the process of highlighting the calibrationpoints 721 a, 721 b. Images of calibration points 721 a, 721 b, . . .and light spots at point-of-aim 210 may be captured during the time whenthe user is engaged in the highlighting process. These images may betemporarily stored, together with the position and orientation of thez′-axis at the time the image was acquired. During the highlightingprocess, it is likely that point-of-aim 210 changes slightly. Theresulting sequence of images may then be used to more accuratelyestimate the orientation and position of the pointing line 21 thatconnects the origin of the x′y′z′ system to calibration point 721 a, 721b, . . . . For example, an averaging algorithm may be used.Alternatively, the stored position and orientation of the z′-axiscorresponding to the captured image for which the light spot atpoint-of-aim 210 is closest to the center of calibration point 721 a,721 b, . . . may be taken as the position and orientation of thepointing line 21 that connects the origin of the x′y′z′ system tocalibration point 721 a, 721 b, . . . .

Some features may also be omitted without affecting the overallapplicability of the present invention. For example, level-sensingdevice (303 in FIG. 1) and visible markings (302 in FIG. 1) may behelpful but are not of critical importance and may be omitted. Iflevel-sensing device 303 are present, the output may also be utilized tocorrect the orientation of the x y z coordinate system to ensure thatits x-y plane is substantially horizontal, as previously explained. Insuch a case, the visible markings 302 may no longer precisely indicatethe position of certain coordinate planes or even the origin of the x yz coordinate system. If the orientation of the uncorrected x-y-planewith respect to a horizontal surface is small enough, though, visiblemarkings 302 may still provide sufficiently reliable information oncoordinate planes and origin of the corrected x y z coordinate system.

Furthermore, the programs outlined in FIGS. 3, 4, 5, 6, 11, 12, 14 and17 may be changed appropriately without loss of functionality,particularly with respect to the order of some of the elements. Theprograms may also be written in any language that is advantageous toparticular the implementation, including without limitation C, Java, andVisual Basic.

Other embodiments that include automatic activation and de-activation oflight-beam projection device 202, or include provision for instructingthe cursor control routines to show or hide computer cursor 501 are alsowithin the scope of the present invention. For example, automaticactivation and de-activation of light-beam projection device 202 mayoccur depending on whether or not the z′-axis intersects one of theinteraction structures 72, or regions of space close to them. This maybe performed by instructions to the cursor control routines to show orhide computer cursor 501. Also, means may be provided to activatelight-beam projection device 202 manually.

Furthermore, pointing device 20 and presentation device 25 may include aconventional, indirect pointing device such as a trackball or the like,to be used in situations where direct pointing is not possible or notdesired. As a practical matter, coordinate sensing device 201, in someembodiments in combination with coordinate sensing device 301, may beused to affect cursor control in an indirect manner if the intended usemakes this desirable. To effect cursor control in indirect pointingapplications, pointing device 20 or presentation device 25 may include auser input device that enables the user to select whether indirectcursor motion control is desired, or may include sensors and/oralgorithms that enable determining when direct pointing actions are notpossible. For example, an algorithm or sensor may be included thatenables determination of whether pointing device 20 or presentationdevice 25 is within the operational range of base station 30. The thirddescribed embodiment, specifically, may be enhanced with algorithmsand/or sensors, such as accelerometers, that enable to determination ofwhether pointing device 20 or presentation device 25 have been displacedsignificantly from the position at which the calibration procedure wasperformed, making direct pointing actions no longer possible withoutadditional calibration steps. As part of the third described embodiment,additional input devices and algorithms may be included that enable theuser to mark an orientation in space such that indirect cursor motioncontrol may be effected based on the changes in orientation with respectto this marked orientation, as described in the cited prior art. Otherembodiments of a system may also be enhanced by such functionality andinput devices.

In addition to the previously described methods to determine size,position and orientation of interaction region 71, other methods arealso within the scope of the invention. These include methods based onthe use of digital cameras and the like. The position and orientation ofsuch cameras, relative to the x y z coordinate system, may be tracked byusing a device such as coordinate sensing device 201 and 301. Forexample, given sufficient knowledge of the optical characteristics of adigital camera, 3D features of an object may be determined from one ormore images taken from one or more positions. Using such images, acomplete 3D description of interaction region 71 may be determined.

Another alternative for establishing 3D position, size and orientationof interaction region 71 is provided by a digital camera or the likeused in addition to, or as embodiment of, the distance measuring device206. In such embodiments the direction relative to the x′y′z′ coordinatesystem of the axis along which distance is measured may be controlledand measured by mounting the digital camera and/or distance measuringdevice 206 in such a way that their orientation relative to the x′y′z′coordinate system may be controlled and measured. Other implementationsin which the foregoing components are positionally fixed are alsocontemplated. For purposes of explanation, the axis along which distanceis measured is denoted as the z″-axis, and the z″=0 position is assumedto coincide with the origin of the x′y′z′ coordinate system. Theorientation of the z″-axis with respect to the x′y′z′ coordinate system,and also with respect to the x y z coordinate system may therefore beassumed to be known. In this embodiment, calibration points 721 a, 721b, . . . may be displayed simultaneously, as projections of screen marks521 a, 521 b, . . . , and may differ in appearance, such that they maybe distinguished by image processing software. Alternatively,calibration points 721 a, 721 b, . . . may appear as projections ofscreen marks 521 a, 521 b, . . . in an automatically controlledsequence. The user may then be queried to direct pointing device 20 inthe general direction of interaction region 71 in such a way that thedigital camera may image the calibration point under consideration. Anautomated calibration sequence may then be executed, wherein the z″-axisis directed, in sequence, to calibration points 721 a, 721 b, . . . etc.The image processing software may identify the various calibrationpoints 721 a, 721 b, . . . and the 3D position of these points may thenbe determined from knowledge of the orientation of the z″-axis and thecoordinates of the z″=0 position with respect to the x y z coordinatesystem, in addition to the measured point-of-aim-distance 211 betweenthe calibration points 721 a, 721 b, . . . and the origin of the x′y′z′coordinate system. This embodiment may also provide light-beamprojection device 202 mounted in a way that enables control of thedirection of the light-beam relative to the x′y′z′ coordinate system.This light-beam may be used to aid in positioning the z″-axis.Embodiments where light-beam projection device 202 are fixed or left outentirely are also contemplated.

FIG. 21A shows the presentation device 25 carried as a headset. FIG. 21Bshows the presentation device 25 being handheld. FIG. 22A shows thepointing device 20 carried as a headset. FIG. 22B shows the pointingdevice 20 being handheld.

The present invention also contemplates situations in which parts of thecalibration procedures outlined may be repeated at appropriate times.For example, when the relative position of base station 30 andinteraction region 71 changes substantially there may be a need torecalibrate the system. Such may also be the case when the position withrespect to interaction region 72 of pointing device 20 or presentationdevice 25 changes significantly, while operation of a particularembodiment of the invention operated using the assumption that suchposition remains substantially unchanged. As another example, coordinatesensing device 201 and/or coordinate sensing device 301 may includetime-integrated acceleration measuring devices. In such a case accuracyof coordinate sensing may deteriorate over time, because of drift in thebase acceleration measurements. When the deterioration has become largeenough to be unacceptable to the user, the user may be queried to placepointing device 20 in certain deemed positions with respect to the x y zcoordinate system, so as to re-initialize coordinate sensing device 201and 301.

The present invention also contemplates the use of a plurality ofpointing devices 20 and/or presentation devices 25. Each of theplurality of pointing devices 20 or presentation devices 25 may beuniquely identifiable by the computer, for example by carrying a uniqueID code inside their respective communication and control device 204.Each of the plurality of pointing or presentation devices may beassociated with a specific cursor and/or a specific interaction region71. For example, a first pointing device may be used to control acorresponding cursor on the left-hand one of two interaction regions 71,and a second pointing device may be used to control a correspondingcursor on the right-hand one of two interaction regions 71.Alternatively, both pointing devices may be used to control acorresponding, identifiable cursor on the same interaction region 71.

Furthermore, the present invention contemplates the use of a pluralityof entities such as base station 30, a particular one of which may beassociated with the origin of the x y z coordinate system. Such a basestation may be designated as the ‘master base station’. Each of the basestations may include coordinate sensing device 201, so that theirrespective position and orientation relative to the master base stationcan be determined with greater accuracy than that afforded by thecoordinate sensing device 201 that is incorporated in pointing device20. Using such multiple base stations and coordinate sensing devices, 3Ddata pertaining to pointing device 20 may be determined relative to theclosest base station, and the relative position and orientation of thatbase station with respect to the master base station may be used toestablish the 3D data pertaining to pointing device 20 with respect tothe x y z coordinate system. Alternatively, signals from multiple basestations, as measured by the coordinate sensing device 201 disposed inpointing device 20, may be used simultaneously to reduce measurementerrors. Generally speaking, determining the 3D data pertaining topointing device 20 with respect to the x y z coordinate system by makinguse of only one base station 30 may be less accurate than by making useof a plurality of base stations. Hence, the effective range′ ofoperation of pointing device 20 may be enhanced by distributing aplurality of base stations over a large region of space.

Referring to FIG. 19, in another embodiment, different devices thanlight-beam projection devices may be used to determine the position ofthe points in set P. For example, light-beam projection device 202 maybe omitted in an embodiment where pointing device 20 has the generalshape of an elongated body, such as a pointing stick. The length of thisstick may be predetermined or variable. For example, pointing device 20could be in the shape of an extendable, or telescopic pen such as theINFINITER Laser Baton sold by Bluesky Marketing—Unit 29, Six HarmonyRow, Glasgow, G51 3 BA, United Kingdom. The process of highlighting acalibration point 721 a 721 b, . . . , in this embodiment may bereplaced by the action of pointing to the calibration point 721 a, 721b, . . . , thereby guided by the elongated shape of pointing device 20instead of the light spot shown in FIG. 18 at point-of-aim 210. Distancemeasuring device 206 may also be provided in a related embodiment,similar to the second described embodiment. For example, distancemeasuring device 206 may include a device to measure the distance fromthe tip of the elongated body of pointing device 20 to the origin of thex′y′z′ coordinate system. In such an embodiment, in order to obtainmeasurements of point-of-aim distance 211, as described for example atprogram element 130 f (see FIG. 12), the user might be queried to makephysical contact between the tip of pointing device 20 and thecalibration point. Referring to FIG. 19, pointing device 20 may alsocomprise contact-sensing device 207, for example at the tip of pointingdevice 20, capable of indicating physical contact between the tip ofpointing device 20 and a surface. Contact-sensing device 207 may be inthe form of a pressure-sensor or switch. Such sensors are known in theart.

The present invention also contemplates the use of various other sensorsintegrated in pointing device 20, presentation device 25 and/or basestation 30 to help determine the position and/or orientation ofinteraction structure 72. For example, pointing device 20, presentationdevice 25 and/or base station 30 may include ultrasonic emitting anddetecting devices to enable measuring substantially the shortestdistance between a known point in the x y z coordinate system (e.g., theposition of pointing device 20; of presentation device 25 or of basestation 30) and the plane in which projection region 60 lies. The usermay be queried to align pointing device 20, presentation device 25 orbase station 30 such that the distance measuring device is orientedsubstantially perpendicularly to projection region 60. It should beunderstood that other types of sensors may be included in pointingdevice 20, presentation device 25 or base station 30 to help constrainthe position and/or orientation of interaction structure 72.

In some cases it may be unnecessary to provide a separately embodiedbase station 30. For example, coordinate sensing device 201 may partlyor completely rely on inertial sensing means such as accelerometers andgyroscopes, or on distance measurements with respect to walls, ceilingand/or floor. In such cases it would be possible to leave out basestation 30 entirely and simply choose an appropriate x y z coordinatesystem. In such embodiments communication and control device 204 couldbe configured to communicate directly with the computer.

The present invention also contemplates the use of automated proceduresto establish the nature of the calibration points 721 a, 721 b, 721 c,721 d, based on the measurements of the orientation and/or position ofthe pointing lines 21 that substantially pass through them. For example,with reference to FIG. 7, calibration points 721 a and 721 d need not beexplicitly identified to the user as upper-right and lower-left cornerrespectively, but may merely be identified as diagonally oppositecorners. Those skilled in the art will appreciate that in such a case anautomated procedure may use the measurements of orientation and/orposition of both pointing lines 21, specifically with respect to thex-y-plane, to identify which of the two lines passes through the upperone of the two diagonally opposite corners. The practical consequence tothe user is that the user need not be concerned about which of the twocalibration points 721 a and 721 d is highlighted first. Similararguments can be used to construct automated procedures that determinewhether a pointing line 21 substantially passes through a left or aright corner of interaction region 71 (and, by assumption, ofinteraction structure 72). For example, the a priori assumption may bemade that the clock-wise angle between a pointing line 21 through a leftcorner and a pointing line 21 through a right corner, measured parallelto the x-y-plane, should not exceed 180 degrees, as will be appreciatedby those skilled in the art.

Finally, although the methods disclosed by the present invention aredescribed in 3D, the invention may also be applied in 2D scenarios.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

What is claimed is:
 1. A non-transitory computer-readable medium ormedia storing computer-executable instructions to direct a computer toperform a method for determining three dimensional features of an objectin conjunction with a first enclosure, the first enclosure configured tobe worn as a headset by a user and comprising: a first accelerometer toprovide a first output, a gyroscope to provide a second output, and adigital camera to provide digital images, the method comprising:determining the three dimensional features of the object based at leastin part on the first output and the second output and two digital imagesprovided by the digital camera, wherein the two digital images are afirst digital image and a second digital image, the first digital imageprovided by the digital camera when the digital camera is at a firstposition, the second digital image provided by the digital camera whenthe digital camera is at a second position that is different from thefirst position; the object has a fixed position relative to a secondenclosure that contains a second accelerometer that provides a thirdoutput; determining the three dimensional futures of the object includesdetermining parameters that are substantially indicative of the threedimensional orientation of the object; and the method furthercalculating positional coordinates of a feature on an image generated bythe computer and further comprising; using the parameters, the firstoutput, the second output, the third output, the first digital image andthe second digital image to calculate the positional coordinates of thefeature on the image.
 2. The non-transitory computer-readable medium ormedia according to claim 1, wherein the image generated by the computeris displayed on a flat surface that has a fixed orientation relative tothe second enclosure, the displayed image is rectangular, the object isa part of the surface where a calibration point is displayed, there isprovided a line with a fixed relation to the first enclosure, thepositional coordinates of the feature correspond to the center of thedisplayed image when the line passes through said center, and thepositional coordinates of the feature correspond to the lower-leftcorner of the displayed image when the line passes through thelower-left corner of a rectangle that has the same center as thedisplayed image and that is two times larger than the displayed image.3. The non-transitory computer-readable medium or media according toclaim 1, wherein the object is a wall, and determining three dimensionalfeatures of the object is determining the distance in three dimensionsbetween the first enclosure and the object.
 4. A non-transitorycomputer-readable medium or media storing computer-executableinstructions to direct a computer to perform a method for determiningthree dimensional features of an object in conjunction with a firstenclosure, the first enclosure configured to be worn as a headset by auser and comprising: a digital camera to provide digital images, a firstaccelerometer to provide a first output, and a gyroscope to provide asecond output, the method comprising: determining the three dimensionalfeatures of the object based at least in part on the first output andthe second output and two digital images provided by the digital camera,wherein the two digital images are a first digital image and a seconddigital image, the first digital image provided by the digital camerawhen the digital camera has a first orientation, the second digitalimage provided by the digital camera when the digital camera has asecond orientation that is different from the first orientation, theobject has a fixed position relative to a human pointing finger,determining the three dimensional features of the object includesestimating parameters that are indicative of the three dimensionalposition of the object; and the method further calculating positionalcoordinates of a feature on an image generated and displayed by thecomputer and further comprising: using parameters, the first output, thesecond output, the first digital image and the second digital image tocalculate the positional coordinates of the feature on the image, andcausing the computer to display the feature on the image.
 5. Anon-transitory computer-readable medium or media storingcomputer-executable instructions to direct a computer to perform amethod for determining three dimensional features of an object inconjunction with a first enclosure, the first enclosure configured to beworn as a headset by a user and comprising: a digital camera to providedigital images, a first accelerometer to provide a first output, and agyroscope to provide a second output, the method comprising: determiningthe three dimensional features of the object based at least in part onthe first output and the second output and two digital images providedby the digital camera, wherein the two digital images are a firstdigital image and a second digital image, the first digital imageprovided by the digital camera when the digital camera has a firstorientation, the second digital image provided by the digital camerawhen the digital camera has a second orientation that is different fromthe first orientation, determining three dimensional features of theobject includes determining parameters that are substantially indicativeof the orientation of the object, the method further calculatingpositional coordinates of a feature that are sensitive to changes inorientation of the first enclosure, the positional coordinates beingrelative to an image generated by the computer, and using theparameters, the first output, the second output, the first digital imageand the second digital image to calculate the positional coordinates ofthe feature on the image.
 6. A non-transitory computer-readable mediumor media storing computer-executable instructions for directing acomputer to perform a method for calculating positional coordinates of afeature on an image in conjunction with an orientation sensing deviceand a digital camera for providing digital images, wherein the computeris for generating the image and for displaying the image on a surface,the positional coordinates are sensitive to orientation of the surface,the orientation sensing device has at least one of a fixed positionrelative to the surface and a fixed orientation relative to the surfaceand for providing an output, and the method comprises the steps of:using an output from the orientation sensing device and an output fromthe digital camera to calculate the positional coordinates of thefeature; and causing the computer to display the image on the surface.7. The non-transitory computer-readable medium or media according toclaim 6, wherein the orientation sensing device comprises anaccelerometer for providing a first output, an enclosure that isdesigned to be wielded by a user in mid-air contains the digital camera,the output from the orientation sensing device is based at least in parton the first output, and the method further comprises the step of: usingat least one digital image provided by the digital camera to calculatethe positional coordinates of the feature.
 8. The non-transitorycomputer-readable medium or media according to claim 7, wherein theorientation sensing device comprises: a gyro for providing a secondoutput and a magnetometer for providing a third output, and the outputfrom the orientation sensing device is based at least in part on thesecond output and the third output.
 9. The non-transitorycomputer-readable medium or media according to claim 8, wherein theenclosure is designed to be worn as a headset and contains theorientation sensing device, the orientation sensing device has a fixedposition relative to the surface, the digital camera is for providing afirst digital image when the digital camera has a first orientation anda second digital image when the digital camera has a second orientationthat is different from the first orientation, and the method furthercomprises the step of: using the first and the second digital image tocalculate the positional coordinates of the feature.
 10. Thenon-transitory computer-readable medium or media according to claim 8,wherein the enclosure is designed to be handheld and contains theorientation sensing device, the orientation sensing device has a fixedposition relative to the surface, the digital camera is for providing afirst digital image when the digital camera has a first orientation anda second digital image when the digital camera has a second orientationthat is different from the first orientation, and the method furthercomprises the step of: using the first and the second digital image tocalculate the positional coordinates of the feature.
 11. Thenon-transitory computer-readable medium or media according to claim 7,wherein the enclosure is designed to be handheld by the user andcontains the orientation sensing device, the enclosure has a fixedposition relative to the surface, the digital camera is for providing afirst digital image when the digital camera has a first orientation anda second digital image when the digital camera has a second orientationthat is different from the first orientation, and the method furthercomprises the step of: using the first and the second digital image tocalculate the positional coordinates of the feature.
 12. Thenon-transitory computer-readable medium or media according to claim 7,wherein the enclosure is designed to be worn as a headset by the userand contains the orientation sensing device, the digital camera is forproviding a first digital image when the digital camera has a firstorientation and a second digital image when the digital camera has asecond orientation that is different from the first orientation, and themethod further comprises the step of: using the first and the seconddigital image to calculate the positional coordinates of the feature.13. A non-transitory computer-readable medium or media storingcomputer-executable instructions for directing a computer to perform amethod for determining three dimensional coordinates of a point using afirst orientation sensing device and a light source, the firstorientation sensing device for sensing orientation of a first line thatis fixed relative to the first orientation sensing device and forproviding an output, the light source for emitting light along a secondline that has a fixed non-zero angle with the first line, and the methodcomprising the steps of: receiving a first output from the firstorientation sensing device; and using the first output and light fromthe light source to determine the coordinates of the point.
 14. Thenon-transitory computer-readable medium or media according to claim 13,wherein the light from the light source substantially coincides with thesecond line.
 15. The non-transitory computer-readable medium or mediaaccording to claim 14, wherein an enclosure that is designed to bewielded in mid-air by a user contains the light source, the firstorientation sensing device, and an image capturing device for providingdigital images, and the method further comprises the step of: using anoutput of the image capturing device to determine the coordinates of thepoint.
 16. The non-transitory computer-readable medium or mediaaccording to claim 15, wherein the output of the image capturing devicecomprises a first and a second digital image; the first digital imagecontaining a first image of a first light-spot generated by the lightsource, the second digital image containing a second image of a secondlight-spot generated by the light source, the first digital image beingdifferent from the second digital image; the method is further forchanging the position of a feature on an image generated by thecomputer, the position being sensitive to orientation of the enclosure;and the method further comprises the steps of: using the first and thesecond digital images to determine the coordinates of the point, andusing the first output to change the position of the feature.
 17. Thenon-transitory computer-readable medium or media according to claim 13,wherein an enclosure that is designed to be worn as a headset by a usercontains the light source, the first orientation sensing and an imagecapturing device, and the method further comprises the step of: using anoutput of the image capturing device to determine the coordinates of thepoint.
 18. The non-transitory computer-readable medium or mediaaccording to claim 13, wherein the light source is an LED, a basestation that is fixed relative to the first line and relative to asurface containing the point contains the first orientation sensingdevice, the computer is for displaying a rectangular image on thesurface, the method further uses a handheld pointing device thatcontains a second orientation sensing device, and the method is forchanging the position of a feature on the image and further comprisesthe steps of: receiving a second output from the second orientationsensing device, the second output being indicative of orientation of athird line that is fixed relative to the second orientation sensingdevice; using the second output to change the position of the feature insuch a way that the feature appears in the top-left corner of the imagewhen the third line passes through the top-left corner of a rectanglethat has the same center and is two times as large as the rectangularimage.